Spring Security Reference

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Spring Security is a framework that provides authentication, authorization, and protection against common attacks.
With first class support for both imperative and reactive applications, it is the de-facto standard for securing Spring-based applications.

Part I. Preface

This section discusses the logistics of Spring Security.

1. Spring Security Community

Welcome to the Spring Security Community!
This section discusses how you to make the most of our vast community.

1.1 Getting Help

If you need help with Spring Security, we are here to help.
Below are some of the best steps to getting help:

1.2 Becoming Involved

We welcome your involvement in the Spring Security project.
There are many ways of contributing, including answering questions on StackOverflow, writing new code, improving existing code, assisting with documentation, developing samples or tutorials, reporting bugs, or simply making suggestions.

2.3 Integrations

@WithMockUsersupports customizing when the SecurityContext is setup in the test.
For example, @WithMockUser(setupBefore = TestExecutionEvent.TEST_EXECUTION) will setup a user after JUnit’s @Before and before the test executes.

Since Spring Boot provides a Maven BOM to manage dependency versions, there is no need to specify a version.
If you wish to override the Spring Security version, you may do so by providing a Maven property:

Since Spring Security only makes breaking changes in major releases, it is safe to use a newer version of Spring Security with Spring Boot.
However, at times it may be necessary to update the version of Spring Framework as well.
This can easily be done by adding a Maven property as well:

If you are using additional features like LDAP, OpenID, etc. you will need to also include the appropriate Chapter 4, Project Modules.

Spring Security builds against Spring Framework 5.1.1.RELEASE, but should generally work with any newer version of Spring Framework 5.x
The problem that many users will have is that Spring Security’s transitive dependencies resolve Spring Framework 5.1.1.RELEASE which can cause strange classpath problems.
The easiest way to resolve this is to use the spring-framework-bom within your <dependencyManagement> section of your pom.xml as shown below:

3.3 Gradle

Like most open source projects, Spring Security deploys its dependencies as Maven artifacts which allows for for first class Gradle support.
The following sections provide details on how to consume Spring Security when using Gradle.

Since Spring Boot provides a Maven BOM to manage dependency versions, there is no need to specify a version.
If you wish to override the Spring Security version, you may do so by providing a Gradle property:

build.gradle.

ext['spring-security.version']='5.1.1.RELEASE'

Since Spring Security only makes breaking changes in major releases, it is safe to use a newer version of Spring Security with Spring Boot.
However, at times it may be necessary to update the version of Spring Framework as well.
This can easily be done by adding a Gradle property as well:

build.gradle.

ext['spring.version']='5.1.1.RELEASE'

If you are using additional features like LDAP, OpenID, etc. you will need to also include the appropriate Chapter 4, Project Modules.

3.3.2 Gradle Without Spring Boot

When using Spring Security without Spring Boot, the preferred way is to leverage Spring Security’s BOM to ensure a consistent version of Spring Security is used throughout the entire project.
This can be done by using the Dependency Management Plugin.

If you are using additional features like LDAP, OpenID, etc. you will need to also include the appropriate Chapter 4, Project Modules.

Spring Security builds against Spring Framework 5.1.1.RELEASE, but should generally work with any newer version of Spring Framework 5.x
The problem that many users will have is that Spring Security’s transitive dependencies resolve Spring Framework 5.1.1.RELEASE which can cause strange classpath problems.
The easiest way to resolve this is to use the spring-framework-bom within your <dependencyManagement> section of your pom.xml as shown below:
This can be done by using the Dependency Management Plugin.

This will ensure that all the transitive dependencies of Spring Security use the Spring 5.1.1.RELEASE modules.

3.3.3 Gradle Repositories

All GA releases (i.e. versions ending in .RELEASE) are deployed to Maven Central, so using the mavenCentral() repository is sufficient for GA releases.

build.gradle.

repositories {
mavenCentral()
}

If you are using a SNAPSHOT version, you will need to ensure you have the Spring Snapshot repository defined as shown below:

build.gradle.

repositories {
maven { url 'https://repo.spring.io/snapshot' }
}

If you are using a milestone or release candidate version, you will need to ensure you have the Spring Milestone repository defined as shown below:

build.gradle.

repositories {
maven { url 'https://repo.spring.io/milestone' }
}

4. Project Modules

In Spring Security 3.0, the codebase has been sub-divided into separate jars which more clearly separate different functionality areas and third-party dependencies.
If you are using Maven to build your project, then these are the modules you will add to your pom.xml.
Even if you’re not using Maven, we’d recommend that you consult the pom.xml files to get an idea of third-party dependencies and versions.
Alternatively, a good idea is to examine the libraries that are included in the sample applications.

4.2 Remoting - spring-security-remoting.jar

Provides intergration with Spring Remoting.
You don’t need this unless you are writing a remote client which uses Spring Remoting.
The main package is org.springframework.security.remoting.

4.3 Web - spring-security-web.jar

Contains filters and related web-security infrastructure code.
Anything with a servlet API dependency.
You’ll need it if you require Spring Security web authentication services and URL-based access-control.
The main package is org.springframework.security.web.

4.4 Config - spring-security-config.jar

Contains the security namespace parsing code & Java configuration code.
You need it if you are using the Spring Security XML namespace for configuration or Spring Security’s Java Configuration support.
The main package is org.springframework.security.config.
None of the classes are intended for direct use in an application.

4.5 LDAP - spring-security-ldap.jar

LDAP authentication and provisioning code.
Required if you need to use LDAP authentication or manage LDAP user entries.
The top-level package is org.springframework.security.ldap.

4.6 OAuth 2.0 Core - spring-security-oauth2-core.jar

spring-security-oauth2-core.jar contains core classes and interfaces that provide support for the OAuth 2.0 Authorization Framework and for OpenID Connect Core 1.0.
It is required by applications that use OAuth 2.0 or OpenID Connect Core 1.0, such as Client, Resource Server, and Authorization Server.
The top-level package is org.springframework.security.oauth2.core.

4.8 OAuth 2.0 JOSE - spring-security-oauth2-jose.jar

spring-security-oauth2-jose.jar contains Spring Security’s support for the JOSE (Javascript Object Signing and Encryption) framework.
The JOSE framework is intended to provide a method to securely transfer claims between parties.
It is built from a collection of specifications:

4.11 OpenID - spring-security-openid.jar

4.12 Test - spring-security-test.jar

Support for testing with Spring Security.

5. Sample Applications

There are several sample web applications that are available with the project.
To avoid an overly large download, only the "tutorial" and "contacts" samples are included in the distribution zip file.
The others can be built directly from the source which you can obtain as described in the introduction.
It’s easy to build the project yourself and there’s more information on the project web site at http://spring.io/spring-security/.
All paths referred to in this chapter are relative to the project source directory.

5.1 Tutorial Sample

The tutorial sample is a nice basic example to get you started.
It uses simple namespace configuration throughout.
The compiled application is included in the distribution zip file, ready to be deployed into your web container (spring-security-samples-tutorial-3.1.x.war).
The form-based authentication mechanism is used in combination with the commonly-used remember-me authentication provider to automatically remember the login using cookies.

We recommend you start with the tutorial sample, as the XML is minimal and easy to follow.
Most importantly, you can easily add this one XML file (and its corresponding web.xml entries) to your existing application.
Only when this basic integration is achieved do we suggest you attempt adding in method authorization or domain object security.

5.2 Contacts

The Contacts Sample is an advanced example in that it illustrates the more powerful features of domain object access control lists (ACLs) in addition to basic application security.
The application provides an interface with which the users are able to administer a simple database of contacts (the domain objects).

To deploy, simply copy the WAR file from Spring Security distribution into your container’s webapps directory.
The war should be called spring-security-samples-contacts-3.1.x.war (the appended version number will vary depending on what release you are using).

After starting your container, check the application can load.
Visit http://localhost:8080/contacts (or whichever URL is appropriate for your web container and the WAR you deployed).

Next, click "Debug".
You will be prompted to authenticate, and a series of usernames and passwords are suggested on that page.
Simply authenticate with any of these and view the resulting page.
It should contain a success message similar to the following:

Once you successfully receive the above message, return to the sample application’s home page and click "Manage".
You can then try out the application.
Notice that only the contacts available to the currently logged on user are displayed, and only users with ROLE_SUPERVISOR are granted access to delete their contacts.
Behind the scenes, the MethodSecurityInterceptor is securing the business objects.

The application allows you to modify the access control lists associated with different contacts.
Be sure to give this a try and understand how it works by reviewing the application context XML files.

5.3 LDAP Sample

The LDAP sample application provides a basic configuration and sets up both a namespace configuration and an equivalent configuration using traditional beans, both in the same application context file.
This means there are actually two identical authentication providers configured in this application.

5.4 OpenID Sample

The OpenID sample demonstrates how to use the namespace to configure OpenID and how to set up attribute exchange configurations for Google, Yahoo and MyOpenID identity providers (you can experiment with adding others if you wish).
It uses the JQuery-based openid-selector project to provide a user-friendly login page which allows the user to easily select a provider, rather than typing in the full OpenID identifier.

The application differs from normal authentication scenarios in that it allows any user to access the site (provided their OpenID authentication is successful).
The first time you login, you will get a "Welcome [your name]"" message.
If you logout and log back in (with the same OpenID identity) then this should change to "Welcome Back".
This is achieved by using a custom UserDetailsService which assigns a standard role to any user and stores the identities internally in a map.
Obviously a real application would use a database instead.
Have a look at the source form more information.
This class also takes into account the fact that different attributes may be returned from different providers and builds the name with which it addresses the user accordingly.

5.5 CAS Sample

The CAS sample requires that you run both a CAS server and CAS client.
It isn’t included in the distribution so you should check out the project code as described in the introduction.
You’ll find the relevant files under the sample/cas directory.
There’s also a Readme.txt file in there which explains how to run both the server and the client directly from the source tree, complete with SSL support.

5.6 JAAS Sample

The JAAS sample is very simple example of how to use a JAAS LoginModule with Spring Security.
The provided LoginModule will successfully authenticate a user if the username equals the password otherwise a LoginException is thrown.
The AuthorityGranter used in this example always grants the role ROLE_USER.
The sample application also demonstrates how to run as the JAAS Subject returned by the LoginModule by setting jaas-api-provision equal to "true".

5.7 Pre-Authentication Sample

This sample application demonstrates how to wire up beans from the pre-authentication framework to make use of login information from a Java EE container.
The user name and roles are those setup by the container.

The code is in samples/preauth.

Part II. Servlet Applications

6. Java Configuration

General support for Java Configuration was added to Spring Framework in Spring 3.1.
Since Spring Security 3.2 there has been Spring Security Java Configuration support which enables users to easily configure Spring Security without the use of any XML.

6.1 Hello Web Security Java Configuration

The first step is to create our Spring Security Java Configuration.
The configuration creates a Servlet Filter known as the springSecurityFilterChain which is responsible for all the security (protecting the application URLs, validating submitted username and passwords, redirecting to the log in form, etc) within your application.
You can find the most basic example of a Spring Security Java Configuration below:

6.1.1 AbstractSecurityWebApplicationInitializer

The next step is to register the springSecurityFilterChain with the war.
This can be done in Java Configuration with Spring’s WebApplicationInitializer support in a Servlet 3.0+ environment.
Not suprisingly, Spring Security provides a base class AbstractSecurityWebApplicationInitializer that will ensure the springSecurityFilterChain gets registered for you.
The way in which we use AbstractSecurityWebApplicationInitializer differs depending on if we are already using Spring or if Spring Security is the only Spring component in our application.

6.1.3 AbstractSecurityWebApplicationInitializer with Spring MVC

If we were using Spring elsewhere in our application we probably already had a WebApplicationInitializer that is loading our Spring Configuration.
If we use the previous configuration we would get an error.
Instead, we should register Spring Security with the existing ApplicationContext.
For example, if we were using Spring MVC our SecurityWebApplicationInitializer would look something like the following:

This would simply only register the springSecurityFilterChain Filter for every URL in your application.
After that we would ensure that WebSecurityConfig was loaded in our existing ApplicationInitializer.
For example, if we were using Spring MVC it would be added in the getRootConfigClasses()

6.2 HttpSecurity

Thus far our WebSecurityConfig only contains information about how to authenticate our users.
How does Spring Security know that we want to require all users to be authenticated? How does Spring Security know we want to support form based authentication? The reason for this is that the WebSecurityConfigurerAdapter provides a default configuration in the configure(HttpSecurity http) method that looks like:

The Java Configuration equivalent of closing an XML tag is expressed using the and() method which allows us to continue configuring the parent.
If you read the code it also makes sense.
I want to configure authorized requests and configure form login and configure HTTP Basic authentication.

6.3 Java Configuration and Form Login

You might be wondering where the login form came from when you were prompted to log in, since we made no mention of any HTML files or JSPs.
Since Spring Security’s default configuration does not explicitly set a URL for the login page, Spring Security generates one automatically, based on the features that are enabled and using standard values for the URL which processes the submitted login, the default target URL the user will be sent to after logging in and so on.

While the automatically generated log in page is convenient to get up and running quickly, most applications will want to provide their own log in page.
To do so we can update our configuration as seen below:

6.4 Authorize Requests

Our examples have only required users to be authenticated and have done so for every URL in our application.
We can specify custom requirements for our URLs by adding multiple children to our http.authorizeRequests() method.
For example:

There are multiple children to the http.authorizeRequests() method each matcher is considered in the order they were declared.

We specified multiple URL patterns that any user can access.
Specifically, any user can access a request if the URL starts with "/resources/", equals "/signup", or equals "/about".

Any URL that starts with "/admin/" will be restricted to users who have the role "ROLE_ADMIN".
You will notice that since we are invoking the hasRole method we do not need to specify the "ROLE_" prefix.

Any URL that starts with "/db/" requires the user to have both "ROLE_ADMIN" and "ROLE_DBA".
You will notice that since we are using the hasRole expression we do not need to specify the "ROLE_" prefix.

Any URL that has not already been matched on only requires that the user be authenticated

6.5 Handling Logouts

When using the WebSecurityConfigurerAdapter, logout capabilities are automatically applied.
The default is that accessing the URL /logout will log the user out by:

Invalidating the HTTP Session

Cleaning up any RememberMe authentication that was configured

Clearing the SecurityContextHolder

Redirect to /login?logout

Similar to configuring login capabilities, however, you also have various options to further customize your logout requirements:

Provides logout support.
This is automatically applied when using WebSecurityConfigurerAdapter.

The URL that triggers log out to occur (default is /logout).
If CSRF protection is enabled (default), then the request must also be a POST.
For more information, please consult the JavaDoc.

The URL to redirect to after logout has occurred.
The default is /login?logout.
For more information, please consult the JavaDoc.

Let’s you specify a custom LogoutSuccessHandler.
If this is specified, logoutSuccessUrl() is ignored.
For more information, please consult the JavaDoc.

Specify whether to invalidate the HttpSession at the time of logout.
This is true by default.
Configures the SecurityContextLogoutHandler under the covers.
For more information, please consult the JavaDoc.

Adds a LogoutHandler.
SecurityContextLogoutHandler is added as the last LogoutHandler by default.

Allows specifying the names of cookies to be removed on logout success.
This is a shortcut for adding a CookieClearingLogoutHandler explicitly.

Note

===
Logouts can of course also be configured using the XML Namespace notation.
Please see the documentation for the logout element in the Spring Security XML Namespace section for further details.
===

Generally, in order to customize logout functionality, you can add
LogoutHandler
and/or
LogoutSuccessHandler
implementations.
For many common scenarios, these handlers are applied under the
covers when using the fluent API.

6.5.1 LogoutHandler

Generally, LogoutHandler
implementations indicate classes that are able to participate in logout handling.
They are expected to be invoked to perform necessary clean-up.
As such they should
not throw exceptions.
Various implementations are provided:

Instead of providing LogoutHandler implementations directly, the fluent API also provides shortcuts that provide the respective LogoutHandler implementations under the covers.
E.g. deleteCookies() allows specifying the names of one or more cookies to be removed on logout success.
This is a shortcut compared to adding a CookieClearingLogoutHandler.

6.5.2 LogoutSuccessHandler

The LogoutSuccessHandler is called after a successful logout by the LogoutFilter, to handle e.g.
redirection or forwarding to the appropriate destination.
Note that the interface is almost the same as the LogoutHandler but may raise an exception.

As mentioned above, you don’t need to specify the SimpleUrlLogoutSuccessHandler directly.
Instead, the fluent API provides a shortcut by setting the logoutSuccessUrl().
This will setup the SimpleUrlLogoutSuccessHandler under the covers.
The provided URL will be redirected to after a logout has occurred.
The default is /login?logout.

The HttpStatusReturningLogoutSuccessHandler can be interesting in REST API type scenarios.
Instead of redirecting to a URL upon the successful logout, this LogoutSuccessHandler allows you to provide a plain HTTP status code to be returned.
If not configured a status code 200 will be returned by default.

HttpSecurity.oauth2Client() provides a number of configuration options for customizing OAuth 2.0 Client.
The following code shows the complete configuration options available for the oauth2Client() DSL:

redirectUriTemplate: The client’s registered redirect URI that the Authorization Server redirects the end-user’s user-agent
to after the end-user has authenticated and authorized access to the client.

scopes: The scope(s) requested by the client during the Authorization Request flow, such as openid, email, or profile.

clientName: A descriptive name used for the client.
The name may be used in certain scenarios, such as when displaying the name of the client in the auto-generated login page.

authorizationUri: The Authorization Endpoint URI for the Authorization Server.

tokenUri: The Token Endpoint URI for the Authorization Server.

jwkSetUri: The URI used to retrieve the JSON Web Key (JWK) Set from the Authorization Server,
which contains the cryptographic key(s) used to verify the JSON Web Signature (JWS) of the ID Token and optionally the UserInfo Response.

configurationMetadata: The OpenID Provider Configuration Information.
This information will only be available if the Spring Boot 2.x property spring.security.oauth2.client.provider.[providerId].issuerUri is configured.

(userInfoEndpoint)uri: The UserInfo Endpoint URI used to access the claims/attributes of the authenticated end-user.

(userInfoEndpoint)authenticationMethod: The authentication method used when sending the access token to the UserInfo Endpoint.
The supported values are header, form and query.

userNameAttributeName: The name of the attribute returned in the UserInfo Response that references the Name or Identifier of the end-user.

6.6.2 ClientRegistrationRepository

Client registration information is ultimately stored and owned by the associated Authorization Server.
This repository provides the ability to retrieve a sub-set of the primary client registration information, which is stored with the Authorization Server.

Spring Boot 2.x auto-configuration binds each of the properties under spring.security.oauth2.client.registration.[registrationId] to an instance of ClientRegistration and then composes each of the ClientRegistration instance(s) within a ClientRegistrationRepository.

Note

The default implementation of ClientRegistrationRepository is InMemoryClientRegistrationRepository.

The auto-configuration also registers the ClientRegistrationRepository as a @Bean in the ApplicationContext so that it is available for dependency-injection, if needed by the application.

6.6.3 OAuth2AuthorizedClient

OAuth2AuthorizedClient is a representation of an Authorized Client.
A client is considered to be authorized when the end-user (Resource Owner) has granted authorization to the client to access its protected resources.

OAuth2AuthorizedClient serves the purpose of associating an OAuth2AccessToken (and optional OAuth2RefreshToken) to a ClientRegistration (client) and resource owner, who is the Principal end-user that granted the authorization.

OAuth2AuthorizedClientRepository is responsible for persisting OAuth2AuthorizedClient(s) between web requests.
Whereas, the primary role of OAuth2AuthorizedClientService is to manage OAuth2AuthorizedClient(s) at the application-level.

From a developer perspective, the OAuth2AuthorizedClientRepository or OAuth2AuthorizedClientService provides the capability to lookup an OAuth2AccessToken associated with a client so that it may be used to initiate a protected resource request.

The developer may also register an OAuth2AuthorizedClientRepository or OAuth2AuthorizedClientService@Bean in the ApplicationContext (overriding Spring Boot 2.x auto-configuration) in order to have the ability to lookup an OAuth2AccessToken associated with a specific ClientRegistration (client).

6.6.5 RegisteredOAuth2AuthorizedClient

The @RegisteredOAuth2AuthorizedClient annotation provides the capability of resolving a method parameter to an argument value of type OAuth2AuthorizedClient.
This is a convenient alternative compared to looking up the OAuth2AuthorizedClient via the OAuth2AuthorizedClientService.

The @RegisteredOAuth2AuthorizedClient annotation is handled by OAuth2AuthorizedClientArgumentResolver and provides the following capabilities:

An OAuth2AccessToken will automatically be requested if the client has not yet been authorized.

For authorization_code, this involves triggering the authorization request redirect to initiate the flow

For client_credentials, the access token is directly obtained from the Token Endpoint using DefaultClientCredentialsTokenResponseClient

6.6.6 AuthorizationRequestRepository

AuthorizationRequestRepository is responsible for the persistence of the OAuth2AuthorizationRequest from the time the Authorization Request is initiated to the time the Authorization Response is received (the callback).

Tip

The OAuth2AuthorizationRequest is used to correlate and validate the Authorization Response.

The default implementation of AuthorizationRequestRepository is HttpSessionOAuth2AuthorizationRequestRepository, which stores the OAuth2AuthorizationRequest in the HttpSession.

If you would like to provide a custom implementation of AuthorizationRequestRepository that stores the attributes of OAuth2AuthorizationRequest in a Cookie, you may configure it as shown in the following example:

6.6.7 OAuth2AuthorizationRequestResolver

The primary role of the OAuth2AuthorizationRequestResolver is to resolve an OAuth2AuthorizationRequest from the provided web request.
The default implementation DefaultOAuth2AuthorizationRequestResolver matches on the (default) path /oauth2/authorization/{registrationId} extracting the registrationId and using it to build the OAuth2AuthorizationRequest for the associated ClientRegistration.

One of the primary use cases an OAuth2AuthorizationRequestResolver can realize is the ability to customize the Authorization Request with additional parameters above the standard parameters defined in the OAuth 2.0 Authorization Framework.

Create a copy of the default OAuth2AuthorizationRequest which returns an OAuth2AuthorizationRequest.Builder for further modifications

Override the default additionalParameters

Tip

OAuth2AuthorizationRequest.Builder.build() constructs the OAuth2AuthorizationRequest.authorizationRequestUri, which represents the complete Authorization Request URI including all query parameters using the application/x-www-form-urlencoded format.

The preceding example shows the common use case of adding a custom parameter on top of the standard parameters.
However, if you need to remove or change a standard parameter or your requirements are more advanced, than you can take full control in building the Authorization Request URI by simply overriding the OAuth2AuthorizationRequest.authorizationRequestUri property.

The following example shows a variation of the customAuthorizationRequest() method from the preceding example, and instead overrides the OAuth2AuthorizationRequest.authorizationRequestUri property.

6.6.8 OAuth2AccessTokenResponseClient

The primary role of the OAuth2AccessTokenResponseClient is to exchange an authorization grant credential for an access token credential at the Authorization Server’s Token Endpoint.

The default implementation of OAuth2AccessTokenResponseClient for the authorization_code grant is DefaultAuthorizationCodeTokenResponseClient, which uses a RestOperations for exchanging an authorization code for an access token at the Token Endpoint.

The DefaultAuthorizationCodeTokenResponseClient is quite flexible as it allows you to customize the pre-processing of the Token Request and/or post-handling of the Token Response.

If you need to customize the pre-processing of the Token Request, you can provide DefaultAuthorizationCodeTokenResponseClient.setRequestEntityConverter() with a custom Converter<OAuth2AuthorizationCodeGrantRequest, RequestEntity<?>>.
The default implementation OAuth2AuthorizationCodeGrantRequestEntityConverter builds a RequestEntity representation of a standard OAuth 2.0 Access Token Request.
However, providing a custom Converter, would allow you to extend the standard Token Request and add a custom parameter for example.

Important

The custom Converter must return a valid RequestEntity representation of an OAuth 2.0 Access Token Request that is understood by the intended OAuth 2.0 Provider.

On the other end, if you need to customize the post-handling of the Token Response, you will need to provide DefaultAuthorizationCodeTokenResponseClient.setRestOperations() with a custom configured RestOperations.
The default RestOperations is configured as follows:

Spring MVC FormHttpMessageConverter is required as it’s used when sending the OAuth 2.0 Access Token Request.

OAuth2AccessTokenResponseHttpMessageConverter is a HttpMessageConverter for an OAuth 2.0 Access Token Response.
You can provide OAuth2AccessTokenResponseHttpMessageConverter.setTokenResponseConverter() with a custom Converter<Map<String, String>, OAuth2AccessTokenResponse> that is used for converting the OAuth 2.0 Access Token Response parameters to an OAuth2AccessTokenResponse.

OAuth2ErrorResponseErrorHandler is a ResponseErrorHandler that can handle an OAuth 2.0 Error (400 Bad Request).
It uses an OAuth2ErrorHttpMessageConverter for converting the OAuth 2.0 Error parameters to an OAuth2Error.

Whether you customize DefaultAuthorizationCodeTokenResponseClient or provide your own implementation of OAuth2AccessTokenResponseClient, you’ll need to configure it as shown in the following example:

6.7 OAuth 2.0 Login

The OAuth 2.0 Login feature provides an application with the capability to have users log in to the application by using their existing account at an OAuth 2.0 Provider (e.g. GitHub) or OpenID Connect 1.0 Provider (such as Google).
OAuth 2.0 Login implements the use cases: "Login with Google" or "Login with GitHub".

Follow the instructions on the OpenID Connect page, starting in the section, "Setting up OAuth 2.0".

After completing the "Obtain OAuth 2.0 credentials" instructions, you should have a new OAuth Client with credentials consisting of a Client ID and a Client Secret.

Setting the redirect URI

The redirect URI is the path in the application that the end-user’s user-agent is redirected back to after they have authenticated with Google and have granted access to the OAuth Client (created in the previous step) on the Consent page.

Replace the values in the client-id and client-secret property with the OAuth 2.0 credentials you created earlier.

Boot up the application

Launch the Spring Boot 2.x sample and go to http://localhost:8080.
You are then redirected to the default auto-generated login page, which displays a link for Google.

Click on the Google link, and you are then redirected to Google for authentication.

After authenticating with your Google account credentials, the next page presented to you is the Consent screen.
The Consent screen asks you to either allow or deny access to the OAuth Client you created earlier.
Click Allow to authorize the OAuth Client to access your email address and basic profile information.

At this point, the OAuth Client retrieves your email address and basic profile information from the UserInfo Endpoint and establishes an authenticated session.

6.7.2 Spring Boot 2.x Property Mappings

The following table outlines the mapping of the Spring Boot 2.x OAuth Client properties to the ClientRegistration properties.

6.8 OAuth 2.0 Resource Server

This is handy in circumstances where an application has federated its authority management out to an authorization server (for example, Okta or Ping Identity).
This authorization server can be consulted by Resource Servers to validate authority when serving requests.

6.8.1 Dependencies

Most Resource Server support is collected into spring-security-oauth2-resource-server.
However, the support for decoding and verifying JWTs is in spring-security-oauth2-jose, meaning that both are necessary in order to have a working resource server that supports JWT-encoded Bearer Tokens.

6.8.2 Minimal Configuration

When using Spring Boot, configuring an application as a resource server consists of two basic steps.
First, include the needed dependencies and second, indicate the location of the authorization server.

Specifying the Authorization Server

Where https://the.issuer.location is the value contained in the iss claim for JWT tokens that the authorization server will issue.
Resource Server will use this property to further self-configure and subsequently validate incoming JWTs.

So long as this scheme is indicated, Resource Server will attempt to process the request according to the Bearer Token specification.

Given a well-formed JWT token, Resource Server will validate the JWTs exp and nbf timestamps and the JWTs iss claim.
It will also validate the signature against a public key obtained from the jwks_url endpoint and matched against the JWTs header.

The resulting Authentication#getPrincipal, by default, is a Spring Security Jwt object, and Authentication#getName map’s to the JWT’s sub property, if one is present.

6.8.3 Specifying the Authorization Server JWK Set Uri Directly

If the authorization server doesn’t support the Provider Configuration endpoint, or if Resource Server must be able to start up independently from the authorization server, then issuer-uri can be exchanged for jwk-set-uri:

The JWK Set uri is not standardized, but can typically be found in the authorization server’s documentation

Consequently, Resource Server will not ping the authorization server at startup.
However, it will also no longer validate the iss claim in the JWT (since Resource Server no longer knows what the issuer value should be).

Extracting Authorities Manually

However, there are a number of circumstances where this default is insufficient.
For example, some authorization server’s don’t use the scope attribute, but instead have their own custom attribute.
Or, at other times, the resource server may need to adapt the attribute or a composition of attributes into internalized authorities.

6.8.6 Configuring Validation

Using minimal Spring Boot configuration, indicating the authorization server’s issuer uri, Resource Server will default to verifying the iss claim as well as the exp and nbf timestamp claims.

In circumstances where validation needs to be customized, Resource Server ships with two standard validators and also accepts custom OAuth2TokenValidator instances.

Customizing Timestamp Validation

JWT’s typically have a window of validity, with the start of the window indicated in the nbf claim and the end indicated in the exp claim.

However, every server can experience clock drift, which can cause tokens to appear expired to one server, but not to another.
This can cause some implementation heartburn as the number of collaborating servers increases in a distributed system.

Resource Server uses JwtTimestampValidator to verify a token’s validity window, and it can be configured with a clockSkew to alleviate the above problem:

6.8.7 Configuring Claim Set Mapping

Spring Security uses the Nimbus library for parsing JWTs and validating their signatures.
Consequently, Spring Security is subject to Nimbus’s interpretation of each field value and how to coerce each into a Java type.

For example, because Nimbus remains Java 7 compatible, it doesn’t use Instant to represent timestamp fields.

And it’s entirely possible to use a different library or for JWT processing, which may make its own coercion decisions that need adjustment.

Or, quite simply, a resource server may want to add or remove claims from a JWT for domain-specific reasons.

For these purposes, Resource Server supports mapping the JWT claim set with MappedJwtClaimSetConverter.

Customizing the Conversion of a Single Claim

By default, MappedJwtClaimSetConverter will attempt to coerce claims into the following types:

Claim

Java Type

aud

Collection<String>

exp

Instant

iat

Instant

iss

URL

jti

String

nbf

Instant

sub

String

An individual claim’s conversion strategy can be configured using MappedJwtClaimSetConverter.withDefaults:

6.9.2 JDBC Authentication

You can find the updates to support JDBC based authentication.
The example below assumes that you have already defined a DataSource within your application.
The jdbc-javaconfig sample provides a complete example of using JDBC based authentication.

6.9.4 AuthenticationProvider

You can define custom authentication by exposing a custom AuthenticationProvider as a bean.
For example, the following will customize authentication assuming that SpringAuthenticationProvider implements AuthenticationProvider:

Note

This is only used if the AuthenticationManagerBuilder has not been populated

6.9.5 UserDetailsService

You can define custom authentication by exposing a custom UserDetailsService as a bean.
For example, the following will customize authentication assuming that SpringDataUserDetailsService implements UserDetailsService:

Note

This is only used if the AuthenticationManagerBuilder has not been populated and no AuthenticationProviderBean is defined.

6.10 Multiple HttpSecurity

We can configure multiple HttpSecurity instances just as we can have multiple <http> blocks.
The key is to extend the WebSecurityConfigurationAdapter multiple times.
For example, the following is an example of having a different configuration for URL’s that start with /api/.

Create an instance of WebSecurityConfigurerAdapter that contains @Order to specify which WebSecurityConfigurerAdapter should be considered first.

The http.antMatcher states that this HttpSecurity will only be applicable to URLs that start with /api/

Create another instance of WebSecurityConfigurerAdapter.
If the URL does not start with /api/ this configuration will be used.
This configuration is considered after ApiWebSecurityConfigurationAdapter since it has an @Order value after 1 (no @Order defaults to last).

6.11 Method Security

From version 2.0 onwards Spring Security has improved support substantially for adding security to your service layer methods.
It provides support for JSR-250 annotation security as well as the framework’s original @Secured annotation.
From 3.0 you can also make use of new expression-based annotations.
You can apply security to a single bean, using the intercept-methods element to decorate the bean declaration, or you can secure multiple beans across the entire service layer using the AspectJ style pointcuts.

6.11.1 EnableGlobalMethodSecurity

We can enable annotation-based security using the @EnableGlobalMethodSecurity annotation on any @Configuration instance.
For example, the following would enable Spring Security’s @Secured annotation.

Adding an annotation to a method (on a class or interface) would then limit the access to that method accordingly.
Spring Security’s native annotation support defines a set of attributes for the method.
These will be passed to the AccessDecisionManager for it to make the actual decision:

6.11.2 GlobalMethodSecurityConfiguration

Sometimes you may need to perform operations that are more complicated than are possible with the @EnableGlobalMethodSecurity annotation allow.
For these instances, you can extend the GlobalMethodSecurityConfiguration ensuring that the @EnableGlobalMethodSecurity annotation is present on your subclass.
For example, if you wanted to provide a custom MethodSecurityExpressionHandler, you could use the following configuration:

For additional information about methods that can be overridden, refer to the GlobalMethodSecurityConfiguration Javadoc.

6.12 Post Processing Configured Objects

Spring Security’s Java Configuration does not expose every property of every object that it configures.
This simplifies the configuration for a majority of users.
Afterall, if every property was exposed, users could use standard bean configuration.

While there are good reasons to not directly expose every property, users may still need more advanced configuration options.
To address this Spring Security introduces the concept of an ObjectPostProcessor which can be used to modify or replace many of the Object instances created by the Java Configuration.
For example, if you wanted to configure the filterSecurityPublishAuthorizationSuccess property on FilterSecurityInterceptor you could use the following:

If you want, you can have WebSecurityConfiguerAdapter add MyCustomDsl by default by using SpringFactories.
For example, you would create a resource on the classpath named META-INF/spring.factories with the following contents:

7. Security Namespace Configuration

7.1 Introduction

Namespace configuration has been available since version 2.0 of the Spring Framework.
It allows you to supplement the traditional Spring beans application context syntax with elements from additional XML schema.
You can find more information in the Spring Reference Documentation.
A namespace element can be used simply to allow a more concise way of configuring an individual bean or, more powerfully, to define an alternative configuration syntax which more closely matches the problem domain and hides the underlying complexity from the user.
A simple element may conceal the fact that multiple beans and processing steps are being added to the application context.
For example, adding the following element from the security namespace to an application context will start up an embedded LDAP server for testing use within the application:

<security:ldap-server />

This is much simpler than wiring up the equivalent Apache Directory Server beans.
The most common alternative configuration requirements are supported by attributes on the ldap-server element and the user is isolated from worrying about which beans they need to create and what the bean property names are.
[1].
Use of a good XML editor while editing the application context file should provide information on the attributes and elements that are available.
We would recommend that you try out the Spring Tool Suite as it has special features for working with standard Spring namespaces.

To start using the security namespace in your application context, you need to have the spring-security-config jar on your classpath.
Then all you need to do is add the schema declaration to your application context file:

In many of the examples you will see (and in the sample applications), we will often use "security" as the default namespace rather than "beans", which means we can omit the prefix on all the security namespace elements, making the content easier to read.
You may also want to do this if you have your application context divided up into separate files and have most of your security configuration in one of them.
Your security application context file would then start like this

7.1.1 Design of the Namespace

The namespace is designed to capture the most common uses of the framework and provide a simplified and concise syntax for enabling them within an application.
The design is based around the large-scale dependencies within the framework, and can be divided up into the following areas:

Web/HTTP Security - the most complex part.
Sets up the filters and related service beans used to apply the framework authentication mechanisms, to secure URLs, render login and error pages and much more.

Business Object (Method) Security - options for securing the service layer.

AuthenticationManager - handles authentication requests from other parts of the framework.

AccessDecisionManager - provides access decisions for web and method security.
A default one will be registered, but you can also choose to use a custom one, declared using normal Spring bean syntax.

AuthenticationProviders - mechanisms against which the authentication manager authenticates users.
The namespace provides supports for several standard options and also a means of adding custom beans declared using a traditional syntax.

UserDetailsService - closely related to authentication providers, but often also required by other beans.

We’ll see how to configure these in the following sections.

7.2 Getting Started with Security Namespace Configuration

In this section, we’ll look at how you can build up a namespace configuration to use some of the main features of the framework.
Let’s assume you initially want to get up and running as quickly as possible and add authentication support and access control to an existing web application, with a few test logins.
Then we’ll look at how to change over to authenticating against a database or other security repository.
In later sections we’ll introduce more advanced namespace configuration options.

7.2.1 web.xml Configuration

The first thing you need to do is add the following filter declaration to your web.xml file:

This provides a hook into the Spring Security web infrastructure.
DelegatingFilterProxy is a Spring Framework class which delegates to a filter implementation which is defined as a Spring bean in your application context.
In this case, the bean is named "springSecurityFilterChain", which is an internal infrastructure bean created by the namespace to handle web security.
Note that you should not use this bean name yourself.
Once you’ve added this to your web.xml, you’re ready to start editing your application context file.
Web security services are configured using the <http> element.

7.2.2 A Minimal <http> Configuration

Which says that we want all URLs within our application to be secured, requiring the role ROLE_USER to access them, we want to log in to the application using a form with username and password, and that we want a logout URL registered which will allow us to log out of the application.
<http> element is the parent for all web-related namespace functionality.
The <intercept-url> element defines a pattern which is matched against the URLs of incoming requests using an ant path style syntax [2].
You can also use regular-expression matching as an alternative (see the namespace appendix for more details).
The access attribute defines the access requirements for requests matching the given pattern.
With the default configuration, this is typically a comma-separated list of roles, one of which a user must have to be allowed to make the request.
The prefix "ROLE_" is a marker which indicates that a simple comparison with the user’s authorities should be made.
In other words, a normal role-based check should be used.
Access-control in Spring Security is not limited to the use of simple roles (hence the use of the prefix to differentiate between different types of security attributes).
We’ll see later how the interpretation can vary footnote:[The interpretation of the comma-separated values in the access attribute depends on the implementation of the 1 which is used.
In Spring Security 3.0, the attribute can also be populated with an 2.

Note

===

You can use multiple <intercept-url> elements to define different access requirements for different sets of URLs, but they will be evaluated in the order listed and the first match will be used.
So you must put the most specific matches at the top.
You can also add a method attribute to limit the match to a particular HTTP method (GET, POST, PUT etc.).

===

To add some users, you can define a set of test data directly in the namespace:

<authentication-manager><authentication-provider><user-service><!-- Password is prefixed with {noop} to indicate to DelegatingPasswordEncoder that
NoOpPasswordEncoder should be used. This is not safe for production, but makes reading
in samples easier. Normally passwords should be hashed using BCrypt --><username="jimi"password="{noop}jimispassword"authorities="ROLE_USER, ROLE_ADMIN" /><username="bob"password="{noop}bobspassword"authorities="ROLE_USER" /></user-service></authentication-provider></authentication-manager>

This is an example of a secure way of storing the same passwords.
The password is prefixed with {bcrypt} to instruct DelegatingPasswordEncoder, which supports any configured PasswordEncoder for matching, that the passwords are hashed using BCrypt:

If you are familiar with pre-namespace versions of the framework, you can probably already guess roughly what’s going on here.
The <http> element is responsible for creating a FilterChainProxy and the filter beans which it uses.
Common problems like incorrect filter ordering are no longer an issue as the filter positions are predefined.

The <authentication-provider> element creates a DaoAuthenticationProvider bean and the <user-service> element creates an InMemoryDaoImpl.
All authentication-provider elements must be children of the <authentication-manager> element, which creates a ProviderManager and registers the authentication providers with it.
You can find more detailed information on the beans that are created in the namespace appendix.
It’s worth cross-checking this if you want to start understanding what the important classes in the framework are and how they are used, particularly if you want to customise things later.

The configuration above defines two users, their passwords and their roles within the application (which will be used for access control).
It is also possible to load user information from a standard properties file using the properties attribute on user-service.
See the section on in-memory authentication for more details on the file format.
Using the <authentication-provider> element means that the user information will be used by the authentication manager to process authentication requests.
You can have multiple <authentication-provider> elements to define different authentication sources and each will be consulted in turn.

At this point you should be able to start up your application and you will be required to log in to proceed.
Try it out, or try experimenting with the "tutorial" sample application that comes with the project.

7.2.3 Form and Basic Login Options

You might be wondering where the login form came from when you were prompted to log in, since we made no mention of any HTML files or JSPs.
In fact, since we didn’t explicitly set a URL for the login page, Spring Security generates one automatically, based on the features that are enabled and using standard values for the URL which processes the submitted login, the default target URL the user will be sent to after logging in and so on.
However, the namespace offers plenty of support to allow you to customize these options.
For example, if you want to supply your own login page, you could use:

Also note that we’ve added an extra intercept-url element to say that any requests for the login page should be available to anonymous users [3] and also the AuthenticatedVoter class for more details on how the value IS_AUTHENTICATED_ANONYMOUSLY is processed.].
Otherwise the request would be matched by the pattern /** and it wouldn’t be possible to access the login page itself!
This is a common configuration error and will result in an infinite loop in the application.
Spring Security will emit a warning in the log if your login page appears to be secured.
It is also possible to have all requests matching a particular pattern bypass the security filter chain completely, by defining a separate http element for the pattern like this:

From Spring Security 3.1 it is now possible to use multiple http elements to define separate security filter chain configurations for different request patterns.
If the pattern attribute is omitted from an http element, it matches all requests.
Creating an unsecured pattern is a simple example of this syntax, where the pattern is mapped to an empty filter chain [4].
We’ll look at this new syntax in more detail in the chapter on the Security Filter Chain.

It’s important to realise that these unsecured requests will be completely oblivious to any Spring Security web-related configuration or additional attributes such as requires-channel, so you will not be able to access information on the current user or call secured methods during the request.
Use access='IS_AUTHENTICATED_ANONYMOUSLY' as an alternative if you still want the security filter chain to be applied.

If you want to use basic authentication instead of form login, then change the configuration to

Basic authentication will then take precedence and will be used to prompt for a login when a user attempts to access a protected resource.
Form login is still available in this configuration if you wish to use it, for example through a login form embedded in another web page.

Setting a Default Post-Login Destination

If a form login isn’t prompted by an attempt to access a protected resource, the default-target-url option comes into play.
This is the URL the user will be taken to after successfully logging in, and defaults to "/".
You can also configure things so that the user always ends up at this page (regardless of whether the login was "on-demand" or they explicitly chose to log in) by setting the always-use-default-target attribute to "true".
This is useful if your application always requires that the user starts at a "home" page, for example:

For even more control over the destination, you can use the authentication-success-handler-ref attribute as an alternative to default-target-url.
The referenced bean should be an instance of AuthenticationSuccessHandler.
You’ll find more on this in the Core Filters chapter and also in the namespace appendix, as well as information on how to customize the flow when authentication fails.

7.2.4 Logout Handling

The logout element adds support for logging out by navigating to a particular URL.
The default logout URL is /logout, but you can set it to something else using the logout-url attribute.
More information on other available attributes may be found in the namespace appendix.

7.2.5 Using other Authentication Providers

In practice you will need a more scalable source of user information than a few names added to the application context file.
Most likely you will want to store your user information in something like a database or an LDAP server.
LDAP namespace configuration is dealt with in the LDAP chapter, so we won’t cover it here.
If you have a custom implementation of Spring Security’s UserDetailsService, called "myUserDetailsService" in your application context, then you can authenticate against this using

Where "securityDataSource" is the name of a DataSource bean in the application context, pointing at a database containing the standard Spring Security user data tables.
Alternatively, you could configure a Spring Security JdbcDaoImpl bean and point at that using the user-service-ref attribute:

where myAuthenticationProvider is the name of a bean in your application context which implements AuthenticationProvider.
You can use multiple authentication-provider elements, in which case the providers will be queried in the order they are declared.
See Section 7.6, “The Authentication Manager and the Namespace” for more information on how the Spring Security AuthenticationManager is configured using the namespace.

Adding a Password Encoder

Passwords should always be encoded using a secure hashing algorithm designed for the purpose (not a standard algorithm like SHA or MD5).
This is supported by the <password-encoder> element.
With bcrypt encoded passwords, the original authentication provider configuration would look like this:

bcrypt is a good choice for most cases, unless you have a legacy system which forces you to use a different algorithm.
If you are using a simple hashing algorithm or, even worse, storing plain text passwords, then you should consider migrating to a more secure option like bcrypt.

7.3 Advanced Web Features

7.3.1 Remember-Me Authentication

7.3.2 Adding HTTP/HTTPS Channel Security

If your application supports both HTTP and HTTPS, and you require that particular URLs can only be accessed over HTTPS, then this is directly supported using the requires-channel attribute on <intercept-url>:

With this configuration in place, if a user attempts to access anything matching the "/secure/**" pattern using HTTP, they will first be redirected to an HTTPS URL [5].
The available options are "http", "https" or "any".
Using the value "any" means that either HTTP or HTTPS can be used.

If your application uses non-standard ports for HTTP and/or HTTPS, you can specify a list of port mappings as follows:

Note that in order to be truly secure, an application should not use HTTP at all or switch between HTTP and HTTPS.
It should start in HTTPS (with the user entering an HTTPS URL) and use a secure connection throughout to avoid any possibility of man-in-the-middle attacks.

7.3.3 Session Management

Detecting Timeouts

You can configure Spring Security to detect the submission of an invalid session ID and redirect the user to an appropriate URL.
This is achieved through the session-management element:

Note that if you use this mechanism to detect session timeouts, it may falsely report an error if the user logs out and then logs back in without closing the browser.
This is because the session cookie is not cleared when you invalidate the session and will be resubmitted even if the user has logged out.
You may be able to explicitly delete the JSESSIONID cookie on logging out, for example by using the following syntax in the logout handler:

<http><logoutdelete-cookies="JSESSIONID" /></http>

Unfortunately this can’t be guaranteed to work with every servlet container, so you will need to test it in your environment

Note

===
If you are running your application behind a proxy, you may also be able to remove the session cookie by configuring the proxy server.
For example, using Apache HTTPD’s mod_headers, the following directive would delete the JSESSIONID cookie by expiring it in the response to a logout request (assuming the application is deployed under the path /tutorial):

Concurrent Session Control

If you wish to place constraints on a single user’s ability to log in to your application, Spring Security supports this out of the box with the following simple additions.
First you need to add the following listener to your web.xml file to keep Spring Security updated about session lifecycle events:

The second login will then be rejected.
By "rejected", we mean that the user will be sent to the authentication-failure-url if form-based login is being used.
If the second authentication takes place through another non-interactive mechanism, such as "remember-me", an "unauthorized" (401) error will be sent to the client.
If instead you want to use an error page, you can add the attribute session-authentication-error-url to the session-management element.

If you are using a customized authentication filter for form-based login, then you have to configure concurrent session control support explicitly.
More details can be found in the Session Management chapter.

Session Fixation Attack Protection

Session fixation attacks are a potential risk where it is possible for a malicious attacker to create a session by accessing a site, then persuade another user to log in with the same session (by sending them a link containing the session identifier as a parameter, for example).
Spring Security protects against this automatically by creating a new session or otherwise changing the session ID when a user logs in.
If you don’t require this protection, or it conflicts with some other requirement, you can control the behavior using the session-fixation-protection attribute on <session-management>, which has four options

none - Don’t do anything.
The original session will be retained.

newSession - Create a new "clean" session, without copying the existing session data (Spring Security-related attributes will still be copied).

migrateSession - Create a new session and copy all existing session attributes to the new session.
This is the default in Servlet 3.0 or older containers.

changeSessionId - Do not create a new session.
Instead, use the session fixation protection provided by the Servlet container (HttpServletRequest#changeSessionId()).
This option is only available in Servlet 3.1 (Java EE 7) and newer containers.
Specifying it in older containers will result in an exception.
This is the default in Servlet 3.1 and newer containers.

When session fixation protection occurs, it results in a SessionFixationProtectionEvent being published in the application context.
If you use changeSessionId, this protection will also result in any javax.servlet.http.HttpSessionIdListener s being notified, so use caution if your code listens for both events.
See the Session Management chapter for additional information.

7.3.4 OpenID Support

The namespace supports OpenID login either instead of, or in addition to normal form-based login, with a simple change:

You should be able to login using the myopenid.com site to authenticate.
It is also possible to select a specific UserDetailsService bean for use OpenID by setting the user-service-ref attribute on the openid-login element.
See the previous section on authentication providers for more information.
Note that we have omitted the password attribute from the above user configuration, since this set of user data is only being used to load the authorities for the user.
A random password will be generated internally, preventing you from accidentally using this user data as an authentication source elsewhere in your configuration.

Attribute Exchange

Support for OpenID attribute exchange.
As an example, the following configuration would attempt to retrieve the email and full name from the OpenID provider, for use by the application:

The "type" of each OpenID attribute is a URI, determined by a particular schema, in this case http://axschema.org/.
If an attribute must be retrieved for successful authentication, the required attribute can be set.
The exact schema and attributes supported will depend on your OpenID provider.
The attribute values are returned as part of the authentication process and can be accessed afterwards using the following code:

The OpenIDAttribute contains the attribute type and the retrieved value (or values in the case of multi-valued attributes).
We’ll see more about how the SecurityContextHolder class is used when we look at core Spring Security components in the technical overview chapter.
Multiple attribute exchange configurations are also be supported, if you wish to use multiple identity providers.
You can supply multiple attribute-exchange elements, using an identifier-matcher attribute on each.
This contains a regular expression which will be matched against the OpenID identifier supplied by the user.
See the OpenID sample application in the codebase for an example configuration, providing different attribute lists for the Google, Yahoo and MyOpenID providers.

7.3.5 Response Headers

7.3.6 Adding in Your Own Filters

If you’ve used Spring Security before, you’ll know that the framework maintains a chain of filters in order to apply its services.
You may want to add your own filters to the stack at particular locations or use a Spring Security filter for which there isn’t currently a namespace configuration option (CAS, for example).
Or you might want to use a customized version of a standard namespace filter, such as the UsernamePasswordAuthenticationFilter which is created by the <form-login> element, taking advantage of some of the extra configuration options which are available by using the bean explicitly.
How can you do this with namespace configuration, since the filter chain is not directly exposed?

The order of the filters is always strictly enforced when using the namespace.
When the application context is being created, the filter beans are sorted by the namespace handling code and the standard Spring Security filters each have an alias in the namespace and a well-known position.

Note

===
In previous versions, the sorting took place after the filter instances had been created, during post-processing of the application context.
In version 3.0+ the sorting is now done at the bean metadata level, before the classes have been instantiated.
This has implications for how you add your own filters to the stack as the entire filter list must be known during the parsing of the <http> element, so the syntax has changed slightly in 3.0.
===

You can also use the after or before attributes if you want your filter to be inserted before or after another filter in the stack.
The names "FIRST" and "LAST" can be used with the position attribute to indicate that you want your filter to appear before or after the entire stack, respectively.

Avoiding filter position conflicts

===

If you are inserting a custom filter which may occupy the same position as one of the standard filters created by the namespace then it’s important that you don’t include the namespace versions by mistake.
Remove any elements which create filters whose functionality you want to replace.

Note that you can’t replace filters which are created by the use of the <http> element itself - SecurityContextPersistenceFilter, ExceptionTranslationFilter or FilterSecurityInterceptor.
Some other filters are added by default, but you can disable them.
An AnonymousAuthenticationFilter is added by default and unless you have session-fixation protection disabled, a SessionManagementFilter will also be added to the filter chain.

===

If you’re replacing a namespace filter which requires an authentication entry point (i.e. where the authentication process is triggered by an attempt by an unauthenticated user to access to a secured resource), you will need to add a custom entry point bean too.

Setting a Custom AuthenticationEntryPoint

If you aren’t using form login, OpenID or basic authentication through the namespace, you may want to define an authentication filter and entry point using a traditional bean syntax and link them into the namespace, as we’ve just seen.
The corresponding AuthenticationEntryPoint can be set using the entry-point-ref attribute on the <http> element.

The CAS sample application is a good example of the use of custom beans with the namespace, including this syntax.
If you aren’t familiar with authentication entry points, they are discussed in the technical overview chapter.

7.4 Method Security

From version 2.0 onwards Spring Security has improved support substantially for adding security to your service layer methods.
It provides support for JSR-250 annotation security as well as the framework’s original @Secured annotation.
From 3.0 you can also make use of new expression-based annotations.
You can apply security to a single bean, using the intercept-methods element to decorate the bean declaration, or you can secure multiple beans across the entire service layer using the AspectJ style pointcuts.

7.4.1 The <global-method-security> Element

This element is used to enable annotation-based security in your application (by setting the appropriate attributes on the element), and also to group together security pointcut declarations which will be applied across your entire application context.
You should only declare one <global-method-security> element.
The following declaration would enable support for Spring Security’s @Secured:

<global-method-securitysecured-annotations="enabled" />

Adding an annotation to a method (on an class or interface) would then limit the access to that method accordingly.
Spring Security’s native annotation support defines a set of attributes for the method.
These will be passed to the AccessDecisionManager for it to make the actual decision:

Expression-based annotations are a good choice if you need to define simple rules that go beyond checking the role names against the user’s list of authorities.

Note

===
The annotated methods will only be secured for instances which are defined as Spring beans (in the same application context in which method-security is enabled).
If you want to secure instances which are not created by Spring (using the new operator, for example) then you need to use AspectJ.
===

Note

===
You can enable more than one type of annotation in the same application, but only one type should be used for any interface or class as the behaviour will not be well-defined otherwise.
If two annotations are found which apply to a particular method, then only one of them will be applied.
===

Adding Security Pointcuts using protect-pointcut

The use of protect-pointcut is particularly powerful, as it allows you to apply security to many beans with only a simple declaration.
Consider the following example:

This will protect all methods on beans declared in the application context whose classes are in the com.mycompany package and whose class names end in "Service".
Only users with the ROLE_USER role will be able to invoke these methods.
As with URL matching, the most specific matches must come first in the list of pointcuts, as the first matching expression will be used.
Security annotations take precedence over pointcuts.

7.5 The Default AccessDecisionManager

This section assumes you have some knowledge of the underlying architecture for access-control within Spring Security.
If you don’t you can skip it and come back to it later, as this section is only really relevant for people who need to do some customization in order to use more than simple role-based security.

When you use a namespace configuration, a default instance of AccessDecisionManager is automatically registered for you and will be used for making access decisions for method invocations and web URL access, based on the access attributes you specify in your intercept-url and protect-pointcut declarations (and in annotations if you are using annotation secured methods).

The default strategy is to use an AffirmativeBasedAccessDecisionManager with a RoleVoter and an AuthenticatedVoter.
You can find out more about these in the chapter on authorization.

7.5.1 Customizing the AccessDecisionManager

If you need to use a more complicated access control strategy then it is easy to set an alternative for both method and web security.

For method security, you do this by setting the access-decision-manager-ref attribute on global-method-security to the id of the appropriate AccessDecisionManager bean in the application context:

7.6 The Authentication Manager and the Namespace

The main interface which provides authentication services in Spring Security is the AuthenticationManager.
This is usually an instance of Spring Security’s ProviderManager class, which you may already be familiar with if you’ve used the framework before.
If not, it will be covered later, in the technical overview chapter.
The bean instance is registered using the authentication-manager namespace element.
You can’t use a custom AuthenticationManager if you are using either HTTP or method security through the namespace, but this should not be a problem as you have full control over the AuthenticationProvider s that are used.

You may want to register additional AuthenticationProvider beans with the ProviderManager and you can do this using the <authentication-provider> element with the ref attribute, where the value of the attribute is the name of the provider bean you want to add.
For example:

Another common requirement is that another bean in the context may require a reference to the AuthenticationManager.
You can easily register an alias for the AuthenticationManager and use this name elsewhere in your application context.

[4] The use of multiple <http> elements is an important feature, allowing the namespace to simultaneously support both stateful and stateless paths within the same application, for example. The previous syntax, using the attribute filters="none" on an intercept-url element is incompatible with this change and is no longer supported in 3.1.

[5] For more details on how channel-processing is implemented, see the Javadoc for ChannelProcessingFilter and related classes.

8. Architecture and Implementation

Once you are familiar with setting up and running some namespace-configuration based applications, you may wish to develop more of an understanding of how the framework actually works behind the namespace facade.
Like most software, Spring Security has certain central interfaces, classes and conceptual abstractions that are commonly used throughout the framework.
In this part of the reference guide we will look at some of these and see how they work together to support authentication and access-control within Spring Security.

8.1 Technical Overview

8.1.1 Runtime Environment

Spring Security 3.0 requires a Java 5.0 Runtime Environment or higher.
As Spring Security aims to operate in a self-contained manner, there is no need to place any special configuration files into your Java Runtime Environment.
In particular, there is no need to configure a special Java Authentication and Authorization Service (JAAS) policy file or place Spring Security into common classpath locations.

Similarly, if you are using an EJB Container or Servlet Container there is no need to put any special configuration files anywhere, nor include Spring Security in a server classloader.
All the required files will be contained within your application.

This design offers maximum deployment time flexibility, as you can simply copy your target artifact (be it a JAR, WAR or EAR) from one system to another and it will immediately work.

8.1.2 Core Components

In Spring Security 3.0, the contents of the spring-security-core jar were stripped down to the bare minimum.
It no longer contains any code related to web-application security, LDAP or namespace configuration.
We’ll take a look here at some of the Java types that you’ll find in the core module.
They represent the building blocks of the framework, so if you ever need to go beyond a simple namespace configuration then it’s important that you understand what they are, even if you don’t actually need to interact with them directly.

SecurityContextHolder, SecurityContext and Authentication Objects

The most fundamental object is SecurityContextHolder.
This is where we store details of the present security context of the application, which includes details of the principal currently using the application.
By default the SecurityContextHolder uses a ThreadLocal to store these details, which means that the security context is always available to methods in the same thread of execution, even if the security context is not explicitly passed around as an argument to those methods.
Using a ThreadLocal in this way is quite safe if care is taken to clear the thread after the present principal’s request is processed.
Of course, Spring Security takes care of this for you automatically so there is no need to worry about it.

Some applications aren’t entirely suitable for using a ThreadLocal, because of the specific way they work with threads.
For example, a Swing client might want all threads in a Java Virtual Machine to use the same security context.
SecurityContextHolder can be configured with a strategy on startup to specify how you would like the context to be stored.
For a standalone application you would use the SecurityContextHolder.MODE_GLOBAL strategy.
Other applications might want to have threads spawned by the secure thread also assume the same security identity.
This is achieved by using SecurityContextHolder.MODE_INHERITABLETHREADLOCAL.
You can change the mode from the default SecurityContextHolder.MODE_THREADLOCAL in two ways.
The first is to set a system property, the second is to call a static method on SecurityContextHolder.
Most applications won’t need to change from the default, but if you do, take a look at the JavaDoc for SecurityContextHolder to learn more.

Obtaining information about the current user

Inside the SecurityContextHolder we store details of the principal currently interacting with the application.
Spring Security uses an Authentication object to represent this information.
You won’t normally need to create an Authentication object yourself, but it is fairly common for users to query the Authentication object.
You can use the following code block - from anywhere in your application - to obtain the name of the currently authenticated user, for example:

The object returned by the call to getContext() is an instance of the SecurityContext interface.
This is the object that is kept in thread-local storage.
As we’ll see below, most authentication mechanisms within Spring Security return an instance of UserDetails as the principal.

The UserDetailsService

Another item to note from the above code fragment is that you can obtain a principal from the Authentication object.
The principal is just an Object.
Most of the time this can be cast into a UserDetails object.
UserDetails is a core interface in Spring Security.
It represents a principal, but in an extensible and application-specific way.
Think of UserDetails as the adapter between your own user database and what Spring Security needs inside the SecurityContextHolder.
Being a representation of something from your own user database, quite often you will cast the UserDetails to the original object that your application provided, so you can call business-specific methods (like getEmail(), getEmployeeNumber() and so on).

By now you’re probably wondering, so when do I provide a UserDetails object? How do I do that? I thought you said this thing was declarative and I didn’t need to write any Java code - what gives? The short answer is that there is a special interface called UserDetailsService.
The only method on this interface accepts a String-based username argument and returns a UserDetails:

This is the most common approach to loading information for a user within Spring Security and you will see it used throughout the framework whenever information on a user is required.

On successful authentication, UserDetails is used to build the Authentication object that is stored in the SecurityContextHolder (more on this below).
The good news is that we provide a number of UserDetailsService implementations, including one that uses an in-memory map (InMemoryDaoImpl) and another that uses JDBC (JdbcDaoImpl).
Most users tend to write their own, though, with their implementations often simply sitting on top of an existing Data Access Object (DAO) that represents their employees, customers, or other users of the application.
Remember the advantage that whatever your UserDetailsService returns can always be obtained from the SecurityContextHolder using the above code fragment.

Note

There is often some confusion about UserDetailsService.
It is purely a DAO for user data and performs no other function other than to supply that data to other components within the framework.
In particular, it does not authenticate the user, which is done by the AuthenticationManager.
In many cases it makes more sense to implement AuthenticationProvider directly if you require a custom authentication process.

GrantedAuthority

Besides the principal, another important method provided by Authentication is getAuthorities().
This method provides an array of GrantedAuthority objects.
A GrantedAuthority is, not surprisingly, an authority that is granted to the principal.
Such authorities are usually "roles", such as ROLE_ADMINISTRATOR or ROLE_HR_SUPERVISOR.
These roles are later on configured for web authorization, method authorization and domain object authorization.
Other parts of Spring Security are capable of interpreting these authorities, and expect them to be present.
GrantedAuthority objects are usually loaded by the UserDetailsService.

Usually the GrantedAuthority objects are application-wide permissions.
They are not specific to a given domain object.
Thus, you wouldn’t likely have a GrantedAuthority to represent a permission to Employee object number 54, because if there are thousands of such authorities you would quickly run out of memory (or, at the very least, cause the application to take a long time to authenticate a user).
Of course, Spring Security is expressly designed to handle this common requirement, but you’d instead use the project’s domain object security capabilities for this purpose.

Summary

Just to recap, the major building blocks of Spring Security that we’ve seen so far are:

SecurityContextHolder, to provide access to the SecurityContext.

SecurityContext, to hold the Authentication and possibly request-specific security information.

Authentication, to represent the principal in a Spring Security-specific manner.

GrantedAuthority, to reflect the application-wide permissions granted to a principal.

UserDetails, to provide the necessary information to build an Authentication object from your application’s DAOs or other source of security data.

UserDetailsService, to create a UserDetails when passed in a String-based username (or certificate ID or the like).

Now that you’ve gained an understanding of these repeatedly-used components, let’s take a closer look at the process of authentication.

8.1.3 Authentication

Spring Security can participate in many different authentication environments.
While we recommend people use Spring Security for authentication and not integrate with existing Container Managed Authentication, it is nevertheless supported - as is integrating with your own proprietary authentication system.

What is authentication in Spring Security?

The system (successfully) verifies that the password is correct for the username.

The context information for that user is obtained (their list of roles and so on).

A security context is established for the user

The user proceeds, potentially to perform some operation which is potentially protected by an access control mechanism which checks the required permissions for the operation against the current security context information.

The first three items constitute the authentication process so we’ll take a look at how these take place within Spring Security.

The username and password are obtained and combined into an instance of UsernamePasswordAuthenticationToken (an instance of the Authentication interface, which we saw earlier).

The token is passed to an instance of AuthenticationManager for validation.

Here we have written a little program that asks the user to enter a username and password and performs the above sequence.
The AuthenticationManager which we’ve implemented here will authenticate any user whose username and password are the same.
It assigns a single role to every user.
The output from the above will be something like:

Note that you don’t normally need to write any code like this.
The process will normally occur internally, in a web authentication filter for example.
We’ve just included the code here to show that the question of what actually constitutes authentication in Spring Security has quite a simple answer.
A user is authenticated when the SecurityContextHolder contains a fully populated Authentication object.

Setting the SecurityContextHolder Contents Directly

In fact, Spring Security doesn’t mind how you put the Authentication object inside the SecurityContextHolder.
The only critical requirement is that the SecurityContextHolder contains an Authentication which represents a principal before the AbstractSecurityInterceptor (which we’ll see more about later) needs to authorize a user operation.

You can (and many users do) write their own filters or MVC controllers to provide interoperability with authentication systems that are not based on Spring Security.
For example, you might be using Container-Managed Authentication which makes the current user available from a ThreadLocal or JNDI location.
Or you might work for a company that has a legacy proprietary authentication system, which is a corporate "standard" over which you have little control.
In situations like this it’s quite easy to get Spring Security to work, and still provide authorization capabilities.
All you need to do is write a filter (or equivalent) that reads the third-party user information from a location, build a Spring Security-specific Authentication object, and put it into the SecurityContextHolder.
In this case you also need to think about things which are normally taken care of automatically by the built-in authentication infrastructure.
For example, you might need to pre-emptively create an HTTP session to cache the context between requests, before you write the response to the client footnote:[It isn’t possible to create a session once the response has been committed.

If you’re wondering how the AuthenticationManager is implemented in a real world example, we’ll look at that in the core services chapter.

8.1.4 Authentication in a Web Application

Now let’s explore the situation where you are using Spring Security in a web application (without web.xml security enabled).
How is a user authenticated and the security context established?

Consider a typical web application’s authentication process:

You visit the home page, and click on a link.

A request goes to the server, and the server decides that you’ve asked for a protected resource.

As you’re not presently authenticated, the server sends back a response indicating that you must authenticate.
The response will either be an HTTP response code, or a redirect to a particular web page.

Depending on the authentication mechanism, your browser will either redirect to the specific web page so that you can fill out the form, or the browser will somehow retrieve your identity (via a BASIC authentication dialogue box, a cookie, a X.509 certificate etc.).

The browser will send back a response to the server.
This will either be an HTTP POST containing the contents of the form that you filled out, or an HTTP header containing your authentication details.

Next the server will decide whether or not the presented credentials are valid.
If they’re valid, the next step will happen.
If they’re invalid, usually your browser will be asked to try again (so you return to step two above).

The original request that you made to cause the authentication process will be retried.
Hopefully you’ve authenticated with sufficient granted authorities to access the protected resource.
If you have sufficient access, the request will be successful.
Otherwise, you’ll receive back an HTTP error code 403, which means "forbidden".

Spring Security has distinct classes responsible for most of the steps described above.
The main participants (in the order that they are used) are the ExceptionTranslationFilter, an AuthenticationEntryPoint and an "authentication mechanism", which is responsible for calling the AuthenticationManager which we saw in the previous section.

ExceptionTranslationFilter

ExceptionTranslationFilter is a Spring Security filter that has responsibility for detecting any Spring Security exceptions that are thrown.
Such exceptions will generally be thrown by an AbstractSecurityInterceptor, which is the main provider of authorization services.
We will discuss AbstractSecurityInterceptor in the next section, but for now we just need to know that it produces Java exceptions and knows nothing about HTTP or how to go about authenticating a principal.
Instead the ExceptionTranslationFilter offers this service, with specific responsibility for either returning error code 403 (if the principal has been authenticated and therefore simply lacks sufficient access - as per step seven above), or launching an AuthenticationEntryPoint (if the principal has not been authenticated and therefore we need to go commence step three).

AuthenticationEntryPoint

The AuthenticationEntryPoint is responsible for step three in the above list.
As you can imagine, each web application will have a default authentication strategy (well, this can be configured like nearly everything else in Spring Security, but let’s keep it simple for now).
Each major authentication system will have its own AuthenticationEntryPoint implementation, which typically performs one of the actions described in step 3.

Authentication Mechanism

Once your browser submits your authentication credentials (either as an HTTP form post or HTTP header) there needs to be something on the server that "collects" these authentication details.
By now we’re at step six in the above list.
In Spring Security we have a special name for the function of collecting authentication details from a user agent (usually a web browser), referring to it as the "authentication mechanism".
Examples are form-base login and Basic authentication.
Once the authentication details have been collected from the user agent, an Authentication "request" object is built and then presented to the AuthenticationManager.

After the authentication mechanism receives back the fully-populated Authentication object, it will deem the request valid, put the Authentication into the SecurityContextHolder, and cause the original request to be retried (step seven above).
If, on the other hand, the AuthenticationManager rejected the request, the authentication mechanism will ask the user agent to retry (step two above).

Storing the SecurityContext between requests

Depending on the type of application, there may need to be a strategy in place to store the security context between user operations.
In a typical web application, a user logs in once and is subsequently identified by their session Id.
The server caches the principal information for the duration session.
In Spring Security, the responsibility for storing the SecurityContext between requests falls to the SecurityContextPersistenceFilter, which by default stores the context as an HttpSession attribute between HTTP requests.
It restores the context to the SecurityContextHolder for each request and, crucially, clears the SecurityContextHolder when the request completes.
You shouldn’t interact directly with the HttpSession for security purposes.
There is simply no justification for doing so - always use the SecurityContextHolder instead.

Many other types of application (for example, a stateless RESTful web service) do not use HTTP sessions and will re-authenticate on every request.
However, it is still important that the SecurityContextPersistenceFilter is included in the chain to make sure that the SecurityContextHolder is cleared after each request.

Note

In an application which receives concurrent requests in a single session, the same SecurityContext instance will be shared between threads.
Even though a ThreadLocal is being used, it is the same instance that is retrieved from the HttpSession for each thread.
This has implications if you wish to temporarily change the context under which a thread is running.
If you just use SecurityContextHolder.getContext(), and call setAuthentication(anAuthentication) on the returned context object, then the Authentication object will change in all concurrent threads which share the same SecurityContext instance.
You can customize the behaviour of SecurityContextPersistenceFilter to create a completely new SecurityContext for each request, preventing changes in one thread from affecting another.
Alternatively you can create a new instance just at the point where you temporarily change the context.
The method SecurityContextHolder.createEmptyContext() always returns a new context instance.

8.1.5 Access-Control (Authorization) in Spring Security

The main interface responsible for making access-control decisions in Spring Security is the AccessDecisionManager.
It has a decide method which takes an Authentication object representing the principal requesting access, a "secure object" (see below) and a list of security metadata attributes which apply for the object (such as a list of roles which are required for access to be granted).

Security and AOP Advice

If you’re familiar with AOP, you’d be aware there are different types of advice available: before, after, throws and around.
An around advice is very useful, because an advisor can elect whether or not to proceed with a method invocation, whether or not to modify the response, and whether or not to throw an exception.
Spring Security provides an around advice for method invocations as well as web requests.
We achieve an around advice for method invocations using Spring’s standard AOP support and we achieve an around advice for web requests using a standard Filter.

For those not familiar with AOP, the key point to understand is that Spring Security can help you protect method invocations as well as web requests.
Most people are interested in securing method invocations on their services layer.
This is because the services layer is where most business logic resides in current-generation Java EE applications.
If you just need to secure method invocations in the services layer, Spring’s standard AOP will be adequate.
If you need to secure domain objects directly, you will likely find that AspectJ is worth considering.

You can elect to perform method authorization using AspectJ or Spring AOP, or you can elect to perform web request authorization using filters.
You can use zero, one, two or three of these approaches together.
The mainstream usage pattern is to perform some web request authorization, coupled with some Spring AOP method invocation authorization on the services layer.

Secure Objects and the AbstractSecurityInterceptor

So what is a "secure object" anyway? Spring Security uses the term to refer to any object that can have security (such as an authorization decision) applied to it.
The most common examples are method invocations and web requests.

Each supported secure object type has its own interceptor class, which is a subclass of AbstractSecurityInterceptor.
Importantly, by the time the AbstractSecurityInterceptor is called, the SecurityContextHolder will contain a valid Authentication if the principal has been authenticated.

Call the AfterInvocationManager if configured, once the invocation has returned.
If the invocation raised an exception, the AfterInvocationManager will not be invoked.

What are Configuration Attributes?

A "configuration attribute" can be thought of as a String that has special meaning to the classes used by AbstractSecurityInterceptor.
They are represented by the interface ConfigAttribute within the framework.
They may be simple role names or have more complex meaning, depending on the how sophisticated the AccessDecisionManager implementation is.
The AbstractSecurityInterceptor is configured with a SecurityMetadataSource which it uses to look up the attributes for a secure object.
Usually this configuration will be hidden from the user.
Configuration attributes will be entered as annotations on secured methods or as access attributes on secured URLs.
For example, when we saw something like <intercept-url pattern='/secure/**' access='ROLE_A,ROLE_B'/> in the namespace introduction, this is saying that the configuration attributes ROLE_A and ROLE_B apply to web requests matching the given pattern.
In practice, with the default AccessDecisionManager configuration, this means that anyone who has a GrantedAuthority matching either of these two attributes will be allowed access.
Strictly speaking though, they are just attributes and the interpretation is dependent on the AccessDecisionManager implementation.
The use of the prefix ROLE_ is a marker to indicate that these attributes are roles and should be consumed by Spring Security’s RoleVoter.
This is only relevant when a voter-based AccessDecisionManager is in use.
We’ll see how the AccessDecisionManager is implemented in the authorization chapter.

RunAsManager

Assuming AccessDecisionManager decides to allow the request, the AbstractSecurityInterceptor will normally just proceed with the request.
Having said that, on rare occasions users may want to replace the Authentication inside the SecurityContext with a different Authentication, which is handled by the AccessDecisionManager calling a RunAsManager.
This might be useful in reasonably unusual situations, such as if a services layer method needs to call a remote system and present a different identity.
Because Spring Security automatically propagates security identity from one server to another (assuming you’re using a properly-configured RMI or HttpInvoker remoting protocol client), this may be useful.

AfterInvocationManager

Following the secure object invocation proceeding and then returning - which may mean a method invocation completing or a filter chain proceeding - the AbstractSecurityInterceptor gets one final chance to handle the invocation.
At this stage the AbstractSecurityInterceptor is interested in possibly modifying the return object.
We might want this to happen because an authorization decision couldn’t be made "on the way in" to a secure object invocation.
Being highly pluggable, AbstractSecurityInterceptor will pass control to an AfterInvocationManager to actually modify the object if needed.
This class can even entirely replace the object, or throw an exception, or not change it in any way as it chooses.
The after-invocation checks will only be executed if the invocation is successful.
If an exception occurs, the additional checks will be skipped.

Extending the Secure Object Model

Only developers contemplating an entirely new way of intercepting and authorizing requests would need to use secure objects directly.
For example, it would be possible to build a new secure object to secure calls to a messaging system.
Anything that requires security and also provides a way of intercepting a call (like the AOP around advice semantics) is capable of being made into a secure object.
Having said that, most Spring applications will simply use the three currently supported secure object types (AOP Alliance MethodInvocation, AspectJ JoinPoint and web request FilterInvocation) with complete transparency.

8.1.6 Localization

Spring Security supports localization of exception messages that end users are likely to see.
If your application is designed for English-speaking users, you don’t need to do anything as by default all Security messages are in English.
If you need to support other locales, everything you need to know is contained in this section.

All exception messages can be localized, including messages related to authentication failures and access being denied (authorization failures).
Exceptions and logging messages that are focused on developers or system deployers (including incorrect attributes, interface contract violations, using incorrect constructors, startup time validation, debug-level logging) are not localized and instead are hard-coded in English within Spring Security’s code.

Shipping in the spring-security-core-xx.jar you will find an org.springframework.security package that in turn contains a messages.properties file, as well as localized versions for some common languages.
This should be referred to by your ApplicationContext, as Spring Security classes implement Spring’s MessageSourceAware interface and expect the message resolver to be dependency injected at application context startup time.
Usually all you need to do is register a bean inside your application context to refer to the messages.
An example is shown below:

The messages.properties is named in accordance with standard resource bundles and represents the default language supported by Spring Security messages.
This default file is in English.

If you wish to customize the messages.properties file, or support other languages, you should copy the file, rename it accordingly, and register it inside the above bean definition.
There are not a large number of message keys inside this file, so localization should not be considered a major initiative.
If you do perform localization of this file, please consider sharing your work with the community by logging a JIRA task and attaching your appropriately-named localized version of messages.properties.

Spring Security relies on Spring’s localization support in order to actually lookup the appropriate message.
In order for this to work, you have to make sure that the locale from the incoming request is stored in Spring’s org.springframework.context.i18n.LocaleContextHolder.
Spring MVC’s DispatcherServlet does this for your application automatically, but since Spring Security’s filters are invoked before this, the LocaleContextHolder needs to be set up to contain the correct Locale before the filters are called.
You can either do this in a filter yourself (which must come before the Spring Security filters in web.xml) or you can use Spring’s RequestContextFilter.
Please refer to the Spring Framework documentation for further details on using localization with Spring.

The "contacts" sample application is set up to use localized messages.

8.2 Core Services

Now that we have a high-level overview of the Spring Security architecture and its core classes, let’s take a closer look at one or two of the core interfaces and their implementations, in particular the AuthenticationManager, UserDetailsService and the AccessDecisionManager.
These crop up regularly throughout the remainder of this document so it’s important you know how they are configured and how they operate.

8.2.1 The AuthenticationManager, ProviderManager and AuthenticationProvider

The AuthenticationManager is just an interface, so the implementation can be anything we choose, but how does it work in practice? What if we need to check multiple authentication databases or a combination of different authentication services such as a database and an LDAP server?

The default implementation in Spring Security is called ProviderManager and rather than handling the authentication request itself, it delegates to a list of configured AuthenticationProvider s, each of which is queried in turn to see if it can perform the authentication.
Each provider will either throw an exception or return a fully populated Authentication object.
Remember our good friends, UserDetails and UserDetailsService? If not, head back to the previous chapter and refresh your memory.
The most common approach to verifying an authentication request is to load the corresponding UserDetails and check the loaded password against the one that has been entered by the user.
This is the approach used by the DaoAuthenticationProvider (see below).
The loaded UserDetails object - and particularly the GrantedAuthority s it contains - will be used when building the fully populated Authentication object which is returned from a successful authentication and stored in the SecurityContext.

If you are using the namespace, an instance of ProviderManager is created and maintained internally, and you add providers to it by using the namespace authentication provider elements (see the namespace chapter).
In this case, you should not declare a ProviderManager bean in your application context.
However, if you are not using the namespace then you would declare it like so:

In the above example we have three providers.
They are tried in the order shown (which is implied by the use of a List), with each provider able to attempt authentication, or skip authentication by simply returning null.
If all implementations return null, the ProviderManager will throw a ProviderNotFoundException.
If you’re interested in learning more about chaining providers, please refer to the ProviderManager Javadoc.

Authentication mechanisms such as a web form-login processing filter are injected with a reference to the ProviderManager and will call it to handle their authentication requests.
The providers you require will sometimes be interchangeable with the authentication mechanisms, while at other times they will depend on a specific authentication mechanism.
For example, DaoAuthenticationProvider and LdapAuthenticationProvider are compatible with any mechanism which submits a simple username/password authentication request and so will work with form-based logins or HTTP Basic authentication.
On the other hand, some authentication mechanisms create an authentication request object which can only be interpreted by a single type of AuthenticationProvider.
An example of this would be JA-SIG CAS, which uses the notion of a service ticket and so can therefore only be authenticated by a CasAuthenticationProvider.
You needn’t be too concerned about this, because if you forget to register a suitable provider, you’ll simply receive a ProviderNotFoundException when an attempt to authenticate is made.

Erasing Credentials on Successful Authentication

By default (from Spring Security 3.1 onwards) the ProviderManager will attempt to clear any sensitive credentials information from the Authentication object which is returned by a successful authentication request.
This prevents information like passwords being retained longer than necessary.

This may cause issues when you are using a cache of user objects, for example, to improve performance in a stateless application.
If the Authentication contains a reference to an object in the cache (such as a UserDetails instance) and this has its credentials removed, then it will no longer be possible to authenticate against the cached value.
You need to take this into account if you are using a cache.
An obvious solution is to make a copy of the object first, either in the cache implementation or in the AuthenticationProvider which creates the returned Authentication object.
Alternatively, you can disable the eraseCredentialsAfterAuthentication property on ProviderManager.
See the Javadoc for more information.

DaoAuthenticationProvider

The simplest AuthenticationProvider implemented by Spring Security is DaoAuthenticationProvider, which is also one of the earliest supported by the framework.
It leverages a UserDetailsService (as a DAO) in order to lookup the username, password and GrantedAuthority s.
It authenticates the user simply by comparing the password submitted in a UsernamePasswordAuthenticationToken against the one loaded by the UserDetailsService.
Configuring the provider is quite simple:

The PasswordEncoder is optional.
A PasswordEncoder provides encoding and decoding of passwords presented in the UserDetails object that is returned from the configured UserDetailsService.
This will be discussed in more detail below.

8.2.2 UserDetailsService Implementations

As mentioned in the earlier in this reference guide, most authentication providers take advantage of the UserDetails and UserDetailsService interfaces.
Recall that the contract for UserDetailsService is a single method:

The returned UserDetails is an interface that provides getters that guarantee non-null provision of authentication information such as the username, password, granted authorities and whether the user account is enabled or disabled.
Most authentication providers will use a UserDetailsService, even if the username and password are not actually used as part of the authentication decision.
They may use the returned UserDetails object just for its GrantedAuthority information, because some other system (like LDAP or X.509 or CAS etc) has undertaken the responsibility of actually validating the credentials.

Given UserDetailsService is so simple to implement, it should be easy for users to retrieve authentication information using a persistence strategy of their choice.
Having said that, Spring Security does include a couple of useful base implementations, which we’ll look at below.

In-Memory Authentication

Is easy to use create a custom UserDetailsService implementation that extracts information from a persistence engine of choice, but many applications do not require such complexity.
This is particularly true if you’re building a prototype application or just starting integrating Spring Security, when you don’t really want to spend time configuring databases or writing UserDetailsService implementations.
For this sort of situation, a simple option is to use the user-service element from the security namespace:

<user-serviceid="userDetailsService"><!-- Password is prefixed with {noop} to indicate to DelegatingPasswordEncoder that
NoOpPasswordEncoder should be used. This is not safe for production, but makes reading
in samples easier. Normally passwords should be hashed using BCrypt --><username="jimi"password="{noop}jimispassword"authorities="ROLE_USER, ROLE_ADMIN" /><username="bob"password="{noop}bobspassword"authorities="ROLE_USER" /></user-service>

JdbcDaoImpl

Spring Security also includes a UserDetailsService that can obtain authentication information from a JDBC data source.
Internally Spring JDBC is used, so it avoids the complexity of a fully-featured object relational mapper (ORM) just to store user details.
If your application does use an ORM tool, you might prefer to write a custom UserDetailsService to reuse the mapping files you’ve probably already created.
Returning to JdbcDaoImpl, an example configuration is shown below:

You can use different relational database management systems by modifying the DriverManagerDataSource shown above.
You can also use a global data source obtained from JNDI, as with any other Spring configuration.

Authority Groups

By default, JdbcDaoImpl loads the authorities for a single user with the assumption that the authorities are mapped directly to users (see the database schema appendix).
An alternative approach is to partition the authorities into groups and assign groups to the user.
Some people prefer this approach as a means of administering user rights.
See the JdbcDaoImpl Javadoc for more information on how to enable the use of group authorities.
The group schema is also included in the appendix.

8.2.3 Password Encoding

Spring Security’s PasswordEncoder interface is used to perform a one way transformation of a password to allow the password to be stored securely.
Given PasswordEncoder is a one way transformation, it is not intended when the password transformation needs to be two way (i.e. storing credentials used to authenticate to a database).
Typically PasswordEncoder is used for storing a password that needs to be compared to a user provided password at the time of authentication.

Password History

Throughout the years the standard mechanism for storing passwords has evolved.
In the beginning passwords were stored in plain text.
The passwords were assumed to be safe because the data store the passwords were saved in required credentials to access it.
However, malicious users were able to find ways to get large "data dumps" of usernames and passwords using attacks like SQL Injection.
As more and more user credentials became public security experts realized we needed to do more to protect users passwords.

Developers were then encouraged to store passwords after running them through a one way hash such as SHA-256.
When a user tried to authenticate, the hashed password would be compared to the hash of the password that they typed.
This meant that the system only needed to store the one way hash of the password.
If a breach occurred, then only the one way hashes of the passwords were exposed.
Since the hashes were one way and it was computationally difficult to guess the passwords given the hash, it would not be worth the effort to figure out each password in the system.
To defeat this new system malicious users decided to create lookup tables known as Rainbow Tables.
Rather than doing the work of guessing each password every time, they computed the password once and stored it in a lookup table.

To mitigate the effectiveness of Rainbow Tables, developers were encouraged to use salted passwords.
Instead of using just the password as input to the hash function, random bytes (known as salt) would be generated for every users' password.
The salt and the user’s password would be ran through the hash function which produced a unique hash.
The salt would be stored alongside the user’s password in clear text.
Then when a user tried to authenticate, the hashed password would be compared to the hash of the stored salt and the password that they typed.
The unique salt meant that Rainbow Tables were no longer effective because the hash was different for every salt and password combination.

In modern times we realize that cryptographic hashes (like SHA-256) are no longer secure.
The reason is that with modern hardware we can perform billions of hash calculations a second.
This means that we can crack each password individually with ease.

Developers are now encouraged to leverage adaptive one-way functions to store a password.
Validation of passwords with adaptive one-way functions are intentionally resource (i.e. CPU, memory, etc) intensive.
An adaptive one-way function allows configuring a "work factor" which can grow as hardware gets better.
It is recommended that the "work factor" be tuned to take about 1 second to verify a password on your system.
This trade off is to make it difficult for attackers to crack the password, but not so costly it puts excessive burden on your own system.
Spring Security has attempted to provide a good starting point for the "work factor", but users are encouraged to customize the "work factor" for their own system since the performance will vary drastically from system to system.
Examples of adaptive one-way functions that should be used include
bcrypt,
PBKDF2,
scrypt,
and Argon2.

Because adaptive one-way functions are intentionally resource intensive, validating a username and password for every request will degrade performance of an application significantly.
There is nothing Spring Security (or any other library) can do to speed up the validation of the password since security is gained by making the validation resource intensive.
Users are encouraged to exchange the long term credentials (i.e. username and password) for a short term credential (i.e. session, OAuth Token, etc).
The short term credential can be validated quickly without any loss in security.

DelegatingPasswordEncoder

Prior to Spring Security 5.0 the default PasswordEncoder was NoOpPasswordEncoder which required plain text passwords.
Based upon the Password History section you might expect that the default PasswordEncoder is now something like BCryptPasswordEncoder.
However, this ignores three real world problems:

There are many applications using old password encodings that cannot easily migrate

The best practice for password storage will change again.

As a framework Spring Security cannot make breaking changes frequently

Instead Spring Security introduces DelegatingPasswordEncoder which solves all of the problems by:

Ensuring that passwords are encoded using the current password storage recommendations

Allowing for validating passwords in modern and legacy formats

Allowing for upgrading the encoding in the future

You can easily construct an instance of DelegatingPasswordEncoder using PasswordEncoderFactories.

Password Storage Format

The general format for a password is:

{id}encodedPassword

Such that id is an identifier used to look up which PasswordEncoder should be used and encodedPassword is the original encoded password for the selected PasswordEncoder.
The id must be at the beginning of the password, start with { and end with }.
If the id cannot be found, the id will be null.
For example, the following might be a list of passwords encoded using different id.
All of the original passwords are "password".

The first password would have a PasswordEncoder id of bcrypt and encodedPassword of $2a$10$dXJ3SW6G7P50lGmMkkmwe.20cQQubK3.HZWzG3YB1tlRy.fqvM/BG.
When matching it would delegate to BCryptPasswordEncoder

The second password would have a PasswordEncoder id of noop and encodedPassword of password.
When matching it would delegate to NoOpPasswordEncoder

The third password would have a PasswordEncoder id of pbkdf2 and encodedPassword of 5d923b44a6d129f3ddf3e3c8d29412723dcbde72445e8ef6bf3b508fbf17fa4ed4d6b99ca763d8dc.
When matching it would delegate to Pbkdf2PasswordEncoder

The fourth password would have a PasswordEncoder id of scrypt and encodedPassword of $e0801$8bWJaSu2IKSn9Z9kM+TPXfOc/9bdYSrN1oD9qfVThWEwdRTnO7re7Ei+fUZRJ68k9lTyuTeUp4of4g24hHnazw==$OAOec05+bXxvuu/1qZ6NUR+xQYvYv7BeL1QxwRpY5Pc=
When matching it would delegate to SCryptPasswordEncoder

The final password would have a PasswordEncoder id of sha256 and encodedPassword of 97cde38028ad898ebc02e690819fa220e88c62e0699403e94fff291cfffaf8410849f27605abcbc0.
When matching it would delegate to StandardPasswordEncoder

Note

Some users might be concerned that the storage format is provided for a potential hacker.
This is not a concern because the storage of the password does not rely on the algorithm being a secret.
Additionally, most formats are easy for an attacker to figure out without the prefix.
For example, BCrypt passwords often start with $2a$.

Password Encoding

The idForEncode passed into the constructor determines which PasswordEncoder will be used for encoding passwords.
In the DelegatingPasswordEncoder we constructed above, that means that the result of encoding password would be delegated to BCryptPasswordEncoder and be prefixed with {bcrypt}.
The end result would look like:

{bcrypt}$2a$10$dXJ3SW6G7P50lGmMkkmwe.20cQQubK3.HZWzG3YB1tlRy.fqvM/BG

Password Matching

Matching is done based upon the {id} and the mapping of the id to the PasswordEncoder provided in the constructor.
Our example in the section called “Password Storage Format” provides a working example of how this is done.
By default, the result of invoking matches(CharSequence, String) with a password and an id that is not mapped (including a null id) will result in an IllegalArgumentException.
This behavior can be customized using DelegatingPasswordEncoder.setDefaultPasswordEncoderForMatches(PasswordEncoder).

By using the id we can match on any password encoding, but encode passwords using the most modern password encoding.
This is important, because unlike encryption, password hashes are designed so that there is no simple way to recover the plaintext.
Since there is no way to recover the plaintext, it makes it difficult to migrate the passwords.
While it is simple for users to migrate NoOpPasswordEncoder, we chose to include it by default to make it simple for the getting started experience.

Getting Started Experience

If you are putting together a demo or a sample, it is a bit cumbersome to take time to hash the passwords of your users.
There are convenience mechanisms to make this easier, but this is still not intended for production.

This does hash the password that is stored, but the passwords are still exposed in memory and in the compiled source code.
Therefore, it is still not considered secure for a production environment.
For production, you should hash your passwords externally.

Troubleshooting

java.lang.IllegalArgumentException: There is no PasswordEncoder mapped for the id "null"
at org.springframework.security.crypto.password.DelegatingPasswordEncoder$UnmappedIdPasswordEncoder.matches(DelegatingPasswordEncoder.java:233)
at org.springframework.security.crypto.password.DelegatingPasswordEncoder.matches(DelegatingPasswordEncoder.java:196)

The easiest way to resolve the error is to switch to explicitly provide the PasswordEncoder that you passwords are encoded with.
The easiest way to resolve it is to figure out how your passwords are currently being stored and explicitly provide the correct PasswordEncoder.
If you are migrating from Spring Security 4.2.x you can revert to the previous behavior by exposing a NoOpPasswordEncoder bean.
For example, if you are using Java Configuration, you can create a configuration that looks like:

Warning

Reverting to NoOpPasswordEncoder is not considered to be secure.
You should instead migrate to using DelegatingPasswordEncoder to support secure password encoding.

Alternatively, you can prefix all of your passwords with the correct id and continue to use DelegatingPasswordEncoder.
For example, if you are using BCrypt, you would migrate your password from something like:

BCryptPasswordEncoder

The BCryptPasswordEncoder implementation uses the widely supported bcrypt algorithm to hash the passwords.
In order to make it more resistent to password cracking, bcrypt is deliberately slow.
Like other adaptive one-way functions, it should be tuned to take about 1 second to verify a password on your system.

Pbkdf2PasswordEncoder

The Pbkdf2PasswordEncoder implementation uses the PBKDF2 algorithm to hash the passwords.
In order to defeat password cracking PBKDF2 is a deliberately slow algorithm.
Like other adaptive one-way functions, it should be tuned to take about 1 second to verify a password on your system.
This algorithm is a good choice when FIPS certification is required.

// Create an encoder with all the defaults
Pbkdf2PasswordEncoder encoder = new Pbkdf2PasswordEncoder();
String result = encoder.encode("myPassword");
assertTrue(encoder.matches("myPassword", result));

SCryptPasswordEncoder

The SCryptPasswordEncoder implementation uses scrypt algorithm to hash the passwords.
In order to defeat password cracking on custom hardware scrypt is a deliberately slow algorithm that requires large amounts of memory.
Like other adaptive one-way functions, it should be tuned to take about 1 second to verify a password on your system.

// Create an encoder with all the defaults
SCryptPasswordEncoder encoder = new SCryptPasswordEncoder();
String result = encoder.encode("myPassword");
assertTrue(encoder.matches("myPassword", result));

Other PasswordEncoders

There are a significant number of other PasswordEncoder implementations that exist entirely for backward compatibility.
They are all deprecated to indicate that they are no longer considered secure.
However, there are no plans to remove them since it is difficult to migrate existing legacy systems.

9.1.1 Security Test Setup

This is a basic example of how to setup Spring Security Test. The highlights are:

@RunWith instructs the spring-test module that it should create an ApplicationContext. This is no different than using the existing Spring Test support. For additional information, refer to the Spring Reference

@ContextConfiguration instructs the spring-test the configuration to use to create the ApplicationContext. Since no configuration is specified, the default configuration locations will be tried. This is no different than using the existing Spring Test support. For additional information, refer to the Spring Reference

Note

Spring Security hooks into Spring Test support using the WithSecurityContextTestExecutionListener which will ensure our tests are ran with the correct user.
It does this by populating the SecurityContextHolder prior to running our tests.
If you are using reactive method security, you will also need ReactorContextTestExecutionListener which populates ReactiveSecurityContextHolder.
After the test is done, it will clear out the SecurityContextHolder.
If you only need Spring Security related support, you can replace @ContextConfiguration with @SecurityTestExecutionListeners.

Remember we added the @PreAuthorize annotation to our HelloMessageService and so it requires an authenticated user to invoke it.
If we ran the following test, we would expect the following test will pass:

9.1.2 @WithMockUser

The question is "How could we most easily run the test as a specific user?"
The answer is to use @WithMockUser.
The following test will be run as a user with the username "user", the password "password", and the roles "ROLE_USER".

The user with the username "user" does not have to exist since we are mocking the user

The Authentication that is populated in the SecurityContext is of type UsernamePasswordAuthenticationToken

The principal on the Authentication is Spring Security’s User object

The User will have the username of "user", the password "password", and a single GrantedAuthority named "ROLE_USER" is used.

Our example is nice because we are able to leverage a lot of defaults.
What if we wanted to run the test with a different username?
The following test would run with the username "customUser". Again, the user does not need to actually exist.

If we do not want the value to automatically be prefixed with ROLE_ we can leverage the authorities attribute.
For example, this test will be invoked with the username "admin" and the authorities "USER" and "ADMIN".

Of course it can be a bit tedious placing the annotation on every test method.
Instead, we can place the annotation at the class level and every test will use the specified user.
For example, the following would run every test with a user with the username "admin", the password "password", and the roles "ROLE_USER" and "ROLE_ADMIN".

By default the SecurityContext is set during the TestExecutionListener.beforeTestMethod event.
This is the equivalent of happening before JUnit’s @Before.
You can change this to happen during the TestExecutionListener.beforeTestExecution event which is after JUnit’s @Before but before the test method is invoked.

@WithMockUser(setupBefore = TestExecutionEvent.TEST_EXECUTION)

9.1.3 @WithAnonymousUser

Using @WithAnonymousUser allows running as an anonymous user.
This is especially convenient when you wish to run most of your tests with a specific user, but want to run a few tests as an anonymous user.
For example, the following will run withMockUser1 and withMockUser2 using @WithMockUser and anonymous as an anonymous user.

By default the SecurityContext is set during the TestExecutionListener.beforeTestMethod event.
This is the equivalent of happening before JUnit’s @Before.
You can change this to happen during the TestExecutionListener.beforeTestExecution event which is after JUnit’s @Before but before the test method is invoked.

@WithAnonymousUser(setupBefore = TestExecutionEvent.TEST_EXECUTION)

9.1.4 @WithUserDetails

While @WithMockUser is a very convenient way to get started, it may not work in all instances.
For example, it is common for applications to expect that the Authentication principal be of a specific type.
This is done so that the application can refer to the principal as the custom type and reduce coupling on Spring Security.

The custom principal is often times returned by a custom UserDetailsService that returns an object that implements both UserDetails and the custom type.
For situations like this, it is useful to create the test user using the custom UserDetailsService.
That is exactly what @WithUserDetails does.

Assuming we have a UserDetailsService exposed as a bean, the following test will be invoked with an Authentication of type UsernamePasswordAuthenticationToken and a principal that is returned from the UserDetailsService with the username of "user".

We can also customize the username used to lookup the user from our UserDetailsService.
For example, this test would be executed with a principal that is returned from the UserDetailsService with the username of "customUsername".

We can also provide an explicit bean name to look up the UserDetailsService.
For example, this test would look up the username of "customUsername" using the UserDetailsService with the bean name "myUserDetailsService".

Like @WithMockUser we can also place our annotation at the class level so that every test uses the same user.
However unlike @WithMockUser, @WithUserDetails requires the user to exist.

By default the SecurityContext is set during the TestExecutionListener.beforeTestMethod event.
This is the equivalent of happening before JUnit’s @Before.
You can change this to happen during the TestExecutionListener.beforeTestExecution event which is after JUnit’s @Before but before the test method is invoked.

@WithUserDetails(setupBefore = TestExecutionEvent.TEST_EXECUTION)

9.1.5 @WithSecurityContext

We have seen that @WithMockUser is an excellent choice if we are not using a custom Authentication principal.
Next we discovered that @WithUserDetails would allow us to use a custom UserDetailsService to create our Authentication principal but required the user to exist.
We will now see an option that allows the most flexibility.

We can create our own annotation that uses the @WithSecurityContext to create any SecurityContext we want.
For example, we might create an annotation named @WithMockCustomUser as shown below:

You can see that @WithMockCustomUser is annotated with the @WithSecurityContext annotation.
This is what signals to Spring Security Test support that we intend to create a SecurityContext for the test.
The @WithSecurityContext annotation requires we specify a SecurityContextFactory that will create a new SecurityContext given our @WithMockCustomUser annotation.
You can find our WithMockCustomUserSecurityContextFactory implementation below:

We can now annotate a test class or a test method with our new annotation and Spring Security’s WithSecurityContextTestExecutionListener will ensure that our SecurityContext is populated appropriately.

When creating your own WithSecurityContextFactory implementations, it is nice to know that they can be annotated with standard Spring annotations.
For example, the WithUserDetailsSecurityContextFactory uses the @Autowired annotation to acquire the UserDetailsService:

By default the SecurityContext is set during the TestExecutionListener.beforeTestMethod event.
This is the equivalent of happening before JUnit’s @Before.
You can change this to happen during the TestExecutionListener.beforeTestExecution event which is after JUnit’s @Before but before the test method is invoked.

@WithSecurityContext(setupBefore = TestExecutionEvent.TEST_EXECUTION)

9.1.6 Test Meta Annotations

If you reuse the same user within your tests often, it is not ideal to have to repeatedly specify the attributes.
For example, if there are many tests related to an administrative user with the username "admin" and the roles ROLE_USER and ROLE_ADMIN you would have to write:

@WithMockUser(username="admin",roles={"USER","ADMIN"})

Rather than repeating this everywhere, we can use a meta annotation.
For example, we could create a meta annotation named WithMockAdmin:

9.2 Spring MVC Test Integration

9.2.1 Setting Up MockMvc and Spring Security

In order to use Spring Security with Spring MVC Test it is necessary to add the Spring Security FilterChainProxy as a Filter.
It is also necessary to add Spring Security’s TestSecurityContextHolderPostProcessor to support Running as a User in Spring MVC Test with Annotations.
This can be done using Spring Security’s SecurityMockMvcConfigurers.springSecurity().
For example:

SecurityMockMvcConfigurers.springSecurity() will perform all of the initial setup we need to integrate Spring Security with Spring MVC Test

9.2.2 SecurityMockMvcRequestPostProcessors

Spring MVC Test provides a convenient interface called a RequestPostProcessor that can be used to modify a request.
Spring Security provides a number of RequestPostProcessor implementations that make testing easier.
In order to use Spring Security’s RequestPostProcessor implementations ensure the following static import is used:

Testing with CSRF Protection

When testing any non-safe HTTP methods and using Spring Security’s CSRF protection, you must be sure to include a valid CSRF Token in the request.
To specify a valid CSRF token as a request parameter using the following:

mvc
.perform(post("/").with(csrf()))

If you like you can include CSRF token in the header instead:

mvc
.perform(post("/").with(csrf().asHeader()))

You can also test providing an invalid CSRF token using the following:

mvc
.perform(post("/").with(csrf().useInvalidToken()))

Running a Test as a User in Spring MVC Test

It is often desirable to run tests as a specific user.
There are two simple ways of populating the user:

Running as a User in Spring MVC Test with RequestPostProcessor

There are a number of options available to associate a user to the current HttpServletRequest.
For example, the following will run as a user (which does not need to exist) with the username "user", the password "password", and the role "ROLE_USER":

Note

The support works by associating the user to the HttpServletRequest.
To associate the request to the SecurityContextHolder you need to ensure that the SecurityContextPersistenceFilter is associated with the MockMvc instance.
A few ways to do this are:

Manually adding SecurityContextPersistenceFilter to the MockMvc instance may make sense when using MockMvcBuilders.standaloneSetup

mvc
.perform(get("/").with(user("user")))

You can easily make customizations.
For example, the following will run as a user (which does not need to exist) with the username "admin", the password "pass", and the roles "ROLE_USER" and "ROLE_ADMIN".

If you have a custom UserDetails that you would like to use, you can easily specify that as well.
For example, the following will use the specified UserDetails (which does not need to exist) to run with a UsernamePasswordAuthenticationToken that has a principal of the specified UserDetails:

mvc
.perform(get("/").with(user(userDetails)))

You can run as anonymous user using the following:

mvc
.perform(get("/").with(anonymous()))

This is especially useful if you are running with a default user and wish to execute a few requests as an anonymous user.

If you want a custom Authentication (which does not need to exist) you can do so using the following:

mvc
.perform(get("/").with(authentication(authentication)))

You can even customize the SecurityContext using the following:

mvc
.perform(get("/").with(securityContext(securityContext)))

We can also ensure to run as a specific user for every request by using MockMvcBuilders's default request.
For example, the following will run as a user (which does not need to exist) with the username "admin", the password "password", and the role "ROLE_ADMIN":

If you find you are using the same user in many of your tests, it is recommended to move the user to a method.
For example, you can specify the following in your own class named CustomSecurityMockMvcRequestPostProcessors:

Running as a User in Spring MVC Test with Annotations

As an alternative to using a RequestPostProcessor to create your user, you can use annotations described in Section 9.1, “Testing Method Security”.
For example, the following will run the test with the user with username "user", password "password", and role "ROLE_USER":

Testing HTTP Basic Authentication

While it has always been possible to authenticate with HTTP Basic, it was a bit tedious to remember the header name, format, and encode the values.
Now this can be done using Spring Security’s httpBasicRequestPostProcessor.
For example, the snippet below:

mvc
.perform(get("/").with(httpBasic("user","password")))

will attempt to use HTTP Basic to authenticate a user with the username "user" and the password "password" by ensuring the following header is populated on the HTTP Request:

Authorization: Basic dXNlcjpwYXNzd29yZA==

9.2.3 SecurityMockMvcRequestBuilders

Spring MVC Test also provides a RequestBuilder interface that can be used to create the MockHttpServletRequest used in your test.
Spring Security provides a few RequestBuilder implementations that can be used to make testing easier.
In order to use Spring Security’s RequestBuilder implementations ensure the following static import is used:

Testing Form Based Authentication

You can easily create a request to test a form based authentication using Spring Security’s testing support.
For example, the following will submit a POST to "/login" with the username "user", the password "password", and a valid CSRF token:

mvc
.perform(formLogin())

It is easy to customize the request.
For example, the following will submit a POST to "/auth" with the username "admin", the password "pass", and a valid CSRF token:

mvc
.perform(formLogin("/auth").user("admin").password("pass"))

We can also customize the parameters names that the username and password are included on.
For example, this is the above request modified to include the username on the HTTP parameter "u" and the password on the HTTP parameter "p".

Testing Logout

While fairly trivial using standard Spring MVC Test, you can use Spring Security’s testing support to make testing log out easier.
For example, the following will submit a POST to "/logout" with a valid CSRF token:

mvc
.perform(logout())

You can also customize the URL to post to.
For example, the snippet below will submit a POST to "/signout" with a valid CSRF token:

mvc
.perform(logout("/signout"))

9.2.4 SecurityMockMvcResultMatchers

At times it is desirable to make various security related assertions about a request.
To accommodate this need, Spring Security Test support implements Spring MVC Test’s ResultMatcher interface.
In order to use Spring Security’s ResultMatcher implementations ensure the following static import is used:

Unauthenticated Assertion

At times it may be valuable to assert that there is no authenticated user associated with the result of a MockMvc invocation.
For example, you might want to test submitting an invalid username and password and verify that no user is authenticated.
You can easily do this with Spring Security’s testing support using something like the following:

Authenticated Assertion

It is often times that we must assert that an authenticated user exists.
For example, we may want to verify that we authenticated successfully.
We could verify that a form based login was successful with the following snippet of code:

mvc
.perform(formLogin())
.andExpect(authenticated());

If we wanted to assert the roles of the user, we could refine our previous code as shown below:

10. Web Application Security

Most Spring Security users will be using the framework in applications which make user of HTTP and the Servlet API.
In this part, we’ll take a look at how Spring Security provides authentication and access-control features for the web layer of an application.
We’ll look behind the facade of the namespace and see which classes and interfaces are actually assembled to provide web-layer security.
In some situations it is necessary to use traditional bean configuration to provide full control over the configuration, so we’ll also see how to configure these classes directly without the namespace.

10.1 The Security Filter Chain

Spring Security’s web infrastructure is based entirely on standard servlet filters.
It doesn’t use servlets or any other servlet-based frameworks (such as Spring MVC) internally, so it has no strong links to any particular web technology.
It deals in HttpServletRequest s and HttpServletResponse s and doesn’t care whether the requests come from a browser, a web service client, an HttpInvoker or an AJAX application.

Spring Security maintains a filter chain internally where each of the filters has a particular responsibility and filters are added or removed from the configuration depending on which services are required.
The ordering of the filters is important as there are dependencies between them.
If you have been using namespace configuration, then the filters are automatically configured for you and you don’t have to define any Spring beans explicitly but here may be times when you want full control over the security filter chain, either because you are using features which aren’t supported in the namespace, or you are using your own customized versions of classes.

10.1.1 DelegatingFilterProxy

When using servlet filters, you obviously need to declare them in your web.xml, or they will be ignored by the servlet container.
In Spring Security, the filter classes are also Spring beans defined in the application context and thus able to take advantage of Spring’s rich dependency-injection facilities and lifecycle interfaces.
Spring’s DelegatingFilterProxy provides the link between web.xml and the application context.

When using DelegatingFilterProxy, you will see something like this in the web.xml file:

Notice that the filter is actually a DelegatingFilterProxy, and not the class that will actually implement the logic of the filter.
What DelegatingFilterProxy does is delegate the Filter 's methods through to a bean which is obtained from the Spring application context.
This enables the bean to benefit from the Spring web application context lifecycle support and configuration flexibility.
The bean must implement javax.servlet.Filter and it must have the same name as that in the filter-name element.
Read the Javadoc for DelegatingFilterProxy for more information

10.1.2 FilterChainProxy

Spring Security’s web infrastructure should only be used by delegating to an instance of FilterChainProxy.
The security filters should not be used by themselves.
In theory you could declare each Spring Security filter bean that you require in your application context file and add a corresponding DelegatingFilterProxy entry to web.xml for each filter, making sure that they are ordered correctly, but this would be cumbersome and would clutter up the web.xml file quickly if you have a lot of filters.
FilterChainProxy lets us add a single entry to web.xml and deal entirely with the application context file for managing our web security beans.
It is wired using a DelegatingFilterProxy, just like in the example above, but with the filter-name set to the bean name "filterChainProxy".
The filter chain is then declared in the application context with the same bean name.
Here’s an example:

The namespace element filter-chain is used for convenience to set up the security filter chain(s) which are required within the application.
[6].
It maps a particular URL pattern to a list of filters built up from the bean names specified in the filters element, and combines them in a bean of type SecurityFilterChain.
The pattern attribute takes an Ant Paths and the most specific URIs should appear first [7].
At runtime the FilterChainProxy will locate the first URI pattern that matches the current web request and the list of filter beans specified by the filters attribute will be applied to that request.
The filters will be invoked in the order they are defined, so you have complete control over the filter chain which is applied to a particular URL.

You may have noticed we have declared two SecurityContextPersistenceFilter s in the filter chain (ASC is short for allowSessionCreation, a property of SecurityContextPersistenceFilter).
As web services will never present a jsessionid on future requests, creating HttpSession s for such user agents would be wasteful.
If you had a high-volume application which required maximum scalability, we recommend you use the approach shown above.
For smaller applications, using a single SecurityContextPersistenceFilter (with its default allowSessionCreation as true) would likely be sufficient.

Note that FilterChainProxy does not invoke standard filter lifecycle methods on the filters it is configured with.
We recommend you use Spring’s application context lifecycle interfaces as an alternative, just as you would for any other Spring bean.

When we looked at how to set up web security using namespace configuration, we used a DelegatingFilterProxy with the name "springSecurityFilterChain".
You should now be able to see that this is the name of the FilterChainProxy which is created by the namespace.

Bypassing the Filter Chain

You can use the attribute filters = "none" as an alternative to supplying a filter bean list.
This will omit the request pattern from the security filter chain entirely.
Note that anything matching this path will then have no authentication or authorization services applied and will be freely accessible.
If you want to make use of the contents of the SecurityContext contents during a request, then it must have passed through the security filter chain.
Otherwise the SecurityContextHolder will not have been populated and the contents will be null.

10.1.3 Filter Ordering

The order that filters are defined in the chain is very important.
Irrespective of which filters you are actually using, the order should be as follows:

ChannelProcessingFilter, because it might need to redirect to a different protocol

SecurityContextPersistenceFilter, so a SecurityContext can be set up in the SecurityContextHolder at the beginning of a web request, and any changes to the SecurityContext can be copied to the HttpSession when the web request ends (ready for use with the next web request)

ConcurrentSessionFilter, because it uses the SecurityContextHolder functionality and needs to update the SessionRegistry to reflect ongoing requests from the principal

Authentication processing mechanisms - UsernamePasswordAuthenticationFilter, CasAuthenticationFilter, BasicAuthenticationFilter etc - so that the SecurityContextHolder can be modified to contain a valid Authentication request token

The SecurityContextHolderAwareRequestFilter, if you are using it to install a Spring Security aware HttpServletRequestWrapper into your servlet container

The JaasApiIntegrationFilter, if a JaasAuthenticationToken is in the SecurityContextHolder this will process the FilterChain as the Subject in the JaasAuthenticationToken

RememberMeAuthenticationFilter, so that if no earlier authentication processing mechanism updated the SecurityContextHolder, and the request presents a cookie that enables remember-me services to take place, a suitable remembered Authentication object will be put there

AnonymousAuthenticationFilter, so that if no earlier authentication processing mechanism updated the SecurityContextHolder, an anonymous Authentication object will be put there

ExceptionTranslationFilter, to catch any Spring Security exceptions so that either an HTTP error response can be returned or an appropriate AuthenticationEntryPoint can be launched

FilterSecurityInterceptor, to protect web URIs and raise exceptions when access is denied

10.1.4 Request Matching and HttpFirewall

Spring Security has several areas where patterns you have defined are tested against incoming requests in order to decide how the request should be handled.
This occurs when the FilterChainProxy decides which filter chain a request should be passed through and also when the FilterSecurityInterceptor decides which security constraints apply to a request.
It’s important to understand what the mechanism is and what URL value is used when testing against the patterns that you define.

The Servlet Specification defines several properties for the HttpServletRequest which are accessible via getter methods, and which we might want to match against.
These are the contextPath, servletPath, pathInfo and queryString.
Spring Security is only interested in securing paths within the application, so the contextPath is ignored.
Unfortunately, the servlet spec does not define exactly what the values of servletPath and pathInfo will contain for a particular request URI.
For example, each path segment of a URL may contain parameters, as defined in RFC 2396[8].
The Specification does not clearly state whether these should be included in the servletPath and pathInfo values and the behaviour varies between different servlet containers.
There is a danger that when an application is deployed in a container which does not strip path parameters from these values, an attacker could add them to the requested URL in order to cause a pattern match to succeed or fail unexpectedly.
[9].
Other variations in the incoming URL are also possible.
For example, it could contain path-traversal sequences (like /../) or multiple forward slashes (//) which could also cause pattern-matches to fail.
Some containers normalize these out before performing the servlet mapping, but others don’t.
To protect against issues like these, FilterChainProxy uses an HttpFirewall strategy to check and wrap the request.
Un-normalized requests are automatically rejected by default, and path parameters and duplicate slashes are removed for matching purposes.
[10].
It is therefore essential that a FilterChainProxy is used to manage the security filter chain.
Note that the servletPath and pathInfo values are decoded by the container, so your application should not have any valid paths which contain semi-colons, as these parts will be removed for matching purposes.

As mentioned above, the default strategy is to use Ant-style paths for matching and this is likely to be the best choice for most users.
The strategy is implemented in the class AntPathRequestMatcher which uses Spring’s AntPathMatcher to perform a case-insensitive match of the pattern against the concatenated servletPath and pathInfo, ignoring the queryString.

If for some reason, you need a more powerful matching strategy, you can use regular expressions.
The strategy implementation is then RegexRequestMatcher.
See the Javadoc for this class for more information.

In practice we recommend that you use method security at your service layer, to control access to your application, and do not rely entirely on the use of security constraints defined at the web-application level.
URLs change and it is difficult to take account of all the possible URLs that an application might support and how requests might be manipulated.
You should try and restrict yourself to using a few simple ant paths which are simple to understand.
Always try to use a "deny-by-default" approach where you have a catch-all wildcard ( / or ) defined last and denying access.

Security defined at the service layer is much more robust and harder to bypass, so you should always take advantage of Spring Security’s method security options.

The HttpFirewall also prevents HTTP Response Splitting by rejecting new line characters in the HTTP Response headers.

By default the StrictHttpFirewall is used.
This implementation rejects requests that appear to be malicious.
If it is too strict for your needs, then you can customize what types of requests are rejected.
However, it is important that you do so knowing that this can open your application up to attacks.
For example, if you wish to leverage Spring MVC’s Matrix Variables, the following configuration could be used in XML:

The StrictHttpFirewall provides a whitelist of valid HTTP methods that are allowed to protect against Cross Site Tracing (XST) and HTTP Verb Tampering.
The default valid methods are "DELETE", "GET", "HEAD", "OPTIONS", "PATCH", "POST", and "PUT".
If your application needs to modify the valid methods, you can configure a custom StrictHttpFirewall bean.
For example, the following will only allow HTTP "GET" and "POST" methods:

If you are using new MockHttpServletRequest() it currently creates an HTTP method as an empty String "".
This is an invalid HTTP method and will be rejected by Spring Security.
You can resolve this by replacing it with new MockHttpServletRequest("GET", "").
See SPR_16851 for an issue requesting to improve this.

If you must allow any HTTP method (not recommended), you can use StrictHttpFirewall.setUnsafeAllowAnyHttpMethod(true).
This will disable validation of the HTTP method entirely.

10.1.5 Use with other Filter-Based Frameworks

If you’re using some other framework that is also filter-based, then you need to make sure that the Spring Security filters come first.
This enables the SecurityContextHolder to be populated in time for use by the other filters.
Examples are the use of SiteMesh to decorate your web pages or a web framework like Wicket which uses a filter to handle its requests.

10.1.6 Advanced Namespace Configuration

As we saw earlier in the namespace chapter, it’s possible to use multiple http elements to define different security configurations for different URL patterns.
Each element creates a filter chain within the internal FilterChainProxy and the URL pattern that should be mapped to it.
The elements will be added in the order they are declared, so the most specific patterns must again be declared first.
Here’s another example, for a similar situation to that above, where the application supports both a stateless RESTful API and also a normal web application which users log into using a form.

10.2 Core Security Filters

There are some key filters which will always be used in a web application which uses Spring Security, so we’ll look at these and their supporting classes and interfaces first.
We won’t cover every feature, so be sure to look at the Javadoc for them if you want to get the complete picture.

10.2.1 FilterSecurityInterceptor

We’ve already seen FilterSecurityInterceptor briefly when discussing access-control in general, and we’ve already used it with the namespace where the <intercept-url> elements are combined to configure it internally.
Now we’ll see how to explicitly configure it for use with a FilterChainProxy, along with its companion filter ExceptionTranslationFilter.
A typical configuration example is shown below:

FilterSecurityInterceptor is responsible for handling the security of HTTP resources.
It requires a reference to an AuthenticationManager and an AccessDecisionManager.
It is also supplied with configuration attributes that apply to different HTTP URL requests.
Refer back to the original discussion on these in the technical introduction.

The FilterSecurityInterceptor can be configured with configuration attributes in two ways.
The first, which is shown above, is using the <filter-security-metadata-source> namespace element.
This is similar to the <http> element from the namespace chapter but the <intercept-url> child elements only use the pattern and access attributes.
Commas are used to delimit the different configuration attributes that apply to each HTTP URL.
The second option is to write your own SecurityMetadataSource, but this is beyond the scope of this document.
Irrespective of the approach used, the SecurityMetadataSource is responsible for returning a List<ConfigAttribute> containing all of the configuration attributes associated with a single secure HTTP URL.

It should be noted that the FilterSecurityInterceptor.setSecurityMetadataSource() method actually expects an instance of FilterInvocationSecurityMetadataSource.
This is a marker interface which subclasses SecurityMetadataSource.
It simply denotes the SecurityMetadataSource understands FilterInvocation s.
In the interests of simplicity we’ll continue to refer to the FilterInvocationSecurityMetadataSource as a SecurityMetadataSource, as the distinction is of little relevance to most users.

The SecurityMetadataSource created by the namespace syntax obtains the configuration attributes for a particular FilterInvocation by matching the request URL against the configured pattern attributes.
This behaves in the same way as it does for namespace configuration.
The default is to treat all expressions as Apache Ant paths and regular expressions are also supported for more complex cases.
The request-matcher attribute is used to specify the type of pattern being used.
It is not possible to mix expression syntaxes within the same definition.
As an example, the previous configuration using regular expressions instead of Ant paths would be written as follows:

Patterns are always evaluated in the order they are defined.
Thus it is important that more specific patterns are defined higher in the list than less specific patterns.
This is reflected in our example above, where the more specific /secure/super/ pattern appears higher than the less specific /secure/ pattern.
If they were reversed, the /secure/ pattern would always match and the /secure/super/ pattern would never be evaluated.

10.2.2 ExceptionTranslationFilter

The ExceptionTranslationFilter sits above the FilterSecurityInterceptor in the security filter stack.
It doesn’t do any actual security enforcement itself, but handles exceptions thrown by the security interceptors and provides suitable and HTTP responses.

AuthenticationEntryPoint

The AuthenticationEntryPoint will be called if the user requests a secure HTTP resource but they are not authenticated.
An appropriate AuthenticationException or AccessDeniedException will be thrown by a security interceptor further down the call stack, triggering the commence method on the entry point.
This does the job of presenting the appropriate response to the user so that authentication can begin.
The one we’ve used here is LoginUrlAuthenticationEntryPoint, which redirects the request to a different URL (typically a login page).
The actual implementation used will depend on the authentication mechanism you want to be used in your application.

AccessDeniedHandler

What happens if a user is already authenticated and they try to access a protected resource? In normal usage, this shouldn’t happen because the application workflow should be restricted to operations to which a user has access.
For example, an HTML link to an administration page might be hidden from users who do not have an admin role.
You can’t rely on hiding links for security though, as there’s always a possibility that a user will just enter the URL directly in an attempt to bypass the restrictions.
Or they might modify a RESTful URL to change some of the argument values.
Your application must be protected against these scenarios or it will definitely be insecure.
You will typically use simple web layer security to apply constraints to basic URLs and use more specific method-based security on your service layer interfaces to really nail down what is permissible.

If an AccessDeniedException is thrown and a user has already been authenticated, then this means that an operation has been attempted for which they don’t have enough permissions.
In this case, ExceptionTranslationFilter will invoke a second strategy, the AccessDeniedHandler.
By default, an AccessDeniedHandlerImpl is used, which just sends a 403 (Forbidden) response to the client.
Alternatively you can configure an instance explicitly (as in the above example) and set an error page URL which it will forwards the request to [11].
This can be a simple "access denied" page, such as a JSP, or it could be a more complex handler such as an MVC controller.
And of course, you can implement the interface yourself and use your own implementation.

It’s also possible to supply a custom AccessDeniedHandler when you’re using the namespace to configure your application.
See the namespace appendix for more details.

SavedRequest s and the RequestCache Interface

Another responsibility of ExceptionTranslationFilter responsibilities is to save the current request before invoking the AuthenticationEntryPoint.
This allows the request to be restored after the user has authenticated (see previous overview of web authentication).
A typical example would be where the user logs in with a form, and is then redirected to the original URL by the default SavedRequestAwareAuthenticationSuccessHandler (see below).

The RequestCache encapsulates the functionality required for storing and retrieving HttpServletRequest instances.
By default the HttpSessionRequestCache is used, which stores the request in the HttpSession.
The RequestCacheFilter has the job of actually restoring the saved request from the cache when the user is redirected to the original URL.

Under normal circumstances, you shouldn’t need to modify any of this functionality, but the saved-request handling is a "best-effort" approach and there may be situations which the default configuration isn’t able to handle.
The use of these interfaces makes it fully pluggable from Spring Security 3.0 onwards.

10.2.3 SecurityContextPersistenceFilter

We covered the purpose of this all-important filter in the Technical Overview chapter so you might want to re-read that section at this point.
Let’s first take a look at how you would configure it for use with a FilterChainProxy.
A basic configuration only requires the bean itself

As we saw previously, this filter has two main tasks.
It is responsible for storage of the SecurityContext contents between HTTP requests and for clearing the SecurityContextHolder when a request is completed.
Clearing the ThreadLocal in which the context is stored is essential, as it might otherwise be possible for a thread to be replaced into the servlet container’s thread pool, with the security context for a particular user still attached.
This thread might then be used at a later stage, performing operations with the wrong credentials.

SecurityContextRepository

From Spring Security 3.0, the job of loading and storing the security context is now delegated to a separate strategy interface:

The HttpRequestResponseHolder is simply a container for the incoming request and response objects, allowing the implementation to replace these with wrapper classes.
The returned contents will be passed to the filter chain.

The default implementation is HttpSessionSecurityContextRepository, which stores the security context as an HttpSession attribute [12].
The most important configuration parameter for this implementation is the allowSessionCreation property, which defaults to true, thus allowing the class to create a session if it needs one to store the security context for an authenticated user (it won’t create one unless authentication has taken place and the contents of the security context have changed).
If you don’t want a session to be created, then you can set this property to false:

Alternatively you could provide an instance of NullSecurityContextRepository, a null object implementation, which will prevent the security context from being stored, even if a session has already been created during the request.

10.2.4 UsernamePasswordAuthenticationFilter

We’ve now seen the three main filters which are always present in a Spring Security web configuration.
These are also the three which are automatically created by the namespace <http> element and cannot be substituted with alternatives.
The only thing that’s missing now is an actual authentication mechanism, something that will allow a user to authenticate.
This filter is the most commonly used authentication filter and the one that is most often customized [13].
It also provides the implementation used by the <form-login> element from the namespace.
There are three stages required to configure it.

Configure a LoginUrlAuthenticationEntryPoint with the URL of the login page, just as we did above, and set it on the ExceptionTranslationFilter.

Implement the login page (using a JSP or MVC controller).

Configure an instance of UsernamePasswordAuthenticationFilter in the application context

The login form simply contains username and password input fields, and posts to the URL that is monitored by the filter (by default this is /login).
The basic filter configuration looks something like this:

Application Flow on Authentication Success and Failure

The filter calls the configured AuthenticationManager to process each authentication request.
The destination following a successful authentication or an authentication failure is controlled by the AuthenticationSuccessHandler and AuthenticationFailureHandler strategy interfaces, respectively.
The filter has properties which allow you to set these so you can customize the behaviour completely [14].
Some standard implementations are supplied such as SimpleUrlAuthenticationSuccessHandler, SavedRequestAwareAuthenticationSuccessHandler, SimpleUrlAuthenticationFailureHandler, ExceptionMappingAuthenticationFailureHandler and DelegatingAuthenticationFailureHandler.
Have a look at the Javadoc for these classes and also for AbstractAuthenticationProcessingFilter to get an overview of how they work and the supported features.

If authentication is successful, the resulting Authentication object will be placed into the SecurityContextHolder.
The configured AuthenticationSuccessHandler will then be called to either redirect or forward the user to the appropriate destination.
By default a SavedRequestAwareAuthenticationSuccessHandler is used, which means that the user will be redirected to the original destination they requested before they were asked to login.

Note

The ExceptionTranslationFilter caches the original request a user makes.
When the user authenticates, the request handler makes use of this cached request to obtain the original URL and redirect to it.
The original request is then rebuilt and used as an alternative.

If authentication fails, the configured AuthenticationFailureHandler will be invoked.

10.3 Servlet API integration

This section describes how Spring Security is integrated with the Servlet API.
The servletapi-xml sample application demonstrates the usage of each of these methods.

10.3.1 Servlet 2.5+ Integration

HttpServletRequest.getRemoteUser()

The HttpServletRequest.getRemoteUser() will return the result of SecurityContextHolder.getContext().getAuthentication().getName() which is typically the current username.
This can be useful if you want to display the current username in your application.
Additionally, checking if this is null can be used to indicate if a user has authenticated or is anonymous.
Knowing if the user is authenticated or not can be useful for determining if certain UI elements should be shown or not (i.e. a log out link should only be displayed if the user is authenticated).

HttpServletRequest.getUserPrincipal()

The HttpServletRequest.getUserPrincipal() will return the result of SecurityContextHolder.getContext().getAuthentication().
This means it is an Authentication which is typically an instance of UsernamePasswordAuthenticationToken when using username and password based authentication.
This can be useful if you need additional information about your user.
For example, you might have created a custom UserDetailsService that returns a custom UserDetails containing a first and last name for your user.
You could obtain this information with the following:

It should be noted that it is typically bad practice to perform so much logic throughout your application.
Instead, one should centralize it to reduce any coupling of Spring Security and the Servlet API’s.

HttpServletRequest.isUserInRole(String)

The HttpServletRequest.isUserInRole(String) will determine if SecurityContextHolder.getContext().getAuthentication().getAuthorities() contains a GrantedAuthority with the role passed into isUserInRole(String).
Typically users should not pass in the "ROLE_" prefix into this method since it is added automatically.
For example, if you want to determine if the current user has the authority "ROLE_ADMIN", you could use the following:

boolean isAdmin = httpServletRequest.isUserInRole("ADMIN");

This might be useful to determine if certain UI components should be displayed.
For example, you might display admin links only if the current user is an admin.

10.3.2 Servlet 3+ Integration

The following section describes the Servlet 3 methods that Spring Security integrates with.

HttpServletRequest.login(String,String)

The HttpServletRequest.login(String,String) method can be used to authenticate the user with the current AuthenticationManager.
For example, the following would attempt to authenticate with the username "user" and password "password":

HttpServletRequest.logout()

Typically this means that the SecurityContextHolder will be cleared out, the HttpSession will be invalidated, any "Remember Me" authentication will be cleaned up, etc.
However, the configured LogoutHandler implementations will vary depending on your Spring Security configuration.
It is important to note that after HttpServletRequest.logout() has been invoked, you are still in charge of writing a response out.
Typically this would involve a redirect to the welcome page.

AsyncContext.start(Runnable)

The AsynchContext.start(Runnable) method that ensures your credentials will be propagated to the new Thread.
Using Spring Security’s concurrency support, Spring Security overrides the AsyncContext.start(Runnable) to ensure that the current SecurityContext is used when processing the Runnable.
For example, the following would output the current user’s Authentication:

Async Servlet Support

If you are using Java Based configuration, you are ready to go.
If you are using XML configuration, there are a few updates that are necessary.
The first step is to ensure you have updated your web.xml to use at least the 3.0 schema as shown below:

That’s it!
Now Spring Security will ensure that your SecurityContext is propagated on asynchronous requests too.

So how does it work? If you are not really interested, feel free to skip the remainder of this section, otherwise read on.
Most of this is built into the Servlet specification, but there is a little bit of tweaking that Spring Security does to ensure things work with asynchronous requests properly.
Prior to Spring Security 3.2, the SecurityContext from the SecurityContextHolder was automatically saved as soon as the HttpServletResponse was committed.
This can cause issues in an Async environment.
For example, consider the following:

The issue is that this Thread is not known to Spring Security, so the SecurityContext is not propagated to it.
This means when we commit the HttpServletResponse there is no SecuriytContext.
When Spring Security automatically saved the SecurityContext on committing the HttpServletResponse it would lose our logged in user.

Since version 3.2, Spring Security is smart enough to no longer automatically save the SecurityContext on commiting the HttpServletResponse as soon as HttpServletRequest.startAsync() is invoked.

10.3.3 Servlet 3.1+ Integration

The following section describes the Servlet 3.1 methods that Spring Security integrates with.

HttpServletRequest#changeSessionId()

10.4 Basic and Digest Authentication

Basic and digest authentication are alternative authentication mechanisms which are popular in web applications.
Basic authentication is often used with stateless clients which pass their credentials on each request.
It’s quite common to use it in combination with form-based authentication where an application is used through both a browser-based user interface and as a web-service.
However, basic authentication transmits the password as plain text so it should only really be used over an encrypted transport layer such as HTTPS.

10.4.1 BasicAuthenticationFilter

BasicAuthenticationFilter is responsible for processing basic authentication credentials presented in HTTP headers.
This can be used for authenticating calls made by Spring remoting protocols (such as Hessian and Burlap), as well as normal browser user agents (such as Firefox and Internet Explorer).
The standard governing HTTP Basic Authentication is defined by RFC 1945, Section 11, and BasicAuthenticationFilter conforms with this RFC.
Basic Authentication is an attractive approach to authentication, because it is very widely deployed in user agents and implementation is extremely simple (it’s just a Base64 encoding of the username:password, specified in an HTTP header).

Configuration

To implement HTTP Basic Authentication, you need to add a BasicAuthenticationFilter to your filter chain.
The application context should contain BasicAuthenticationFilter and its required collaborator:

The configured AuthenticationManager processes each authentication request.
If authentication fails, the configured AuthenticationEntryPoint will be used to retry the authentication process.
Usually you will use the filter in combination with a BasicAuthenticationEntryPoint, which returns a 401 response with a suitable header to retry HTTP Basic authentication.
If authentication is successful, the resulting Authentication object will be placed into the SecurityContextHolder as usual.

If the authentication event was successful, or authentication was not attempted because the HTTP header did not contain a supported authentication request, the filter chain will continue as normal.
The only time the filter chain will be interrupted is if authentication fails and the AuthenticationEntryPoint is called.

10.4.2 DigestAuthenticationFilter

DigestAuthenticationFilter is capable of processing digest authentication credentials presented in HTTP headers.
Digest Authentication attempts to solve many of the weaknesses of Basic authentication, specifically by ensuring credentials are never sent in clear text across the wire.
Many user agents support Digest Authentication, including Mozilla Firefox and Internet Explorer.
The standard governing HTTP Digest Authentication is defined by RFC 2617, which updates an earlier version of the Digest Authentication standard prescribed by RFC 2069.
Most user agents implement RFC 2617.
Spring Security’s DigestAuthenticationFilter is compatible with the “auth” quality of protection (qop) prescribed by RFC 2617, which also provides backward compatibility with RFC 2069.
Digest Authentication is a more attractive option if you need to use unencrypted HTTP (i.e. no TLS/HTTPS) and wish to maximise security of the authentication process.
Indeed Digest Authentication is a mandatory requirement for the WebDAV protocol, as noted by RFC 2518 Section 17.1.

Note

You should not use Digest in modern applications because it is not considered secure.
The most obvious problem is that you must store your passwords in plaintext, encrypted, or an MD5 format.
All of these storage formats are considered insecure.
Instead, you should use a one way adaptive password hash (i.e. bCrypt, PBKDF2, SCrypt, etc).

Central to Digest Authentication is a "nonce".
This is a value the server generates.
Spring Security’s nonce adopts the following format:

base64(expirationTime + ":" + md5Hex(expirationTime + ":" + key))
expirationTime: The date and time when the nonce expires, expressed in milliseconds
key: A private key to prevent modification of the nonce token

The DigestAuthenticatonEntryPoint has a property specifying the key used for generating the nonce tokens, along with a nonceValiditySeconds property for determining the expiration time (default 300, which equals five minutes).
Whist ever the nonce is valid, the digest is computed by concatenating various strings including the username, password, nonce, URI being requested, a client-generated nonce (merely a random value which the user agent generates each request), the realm name etc, then performing an MD5 hash.
Both the server and user agent perform this digest computation, resulting in different hash codes if they disagree on an included value (eg password).
In Spring Security implementation, if the server-generated nonce has merely expired (but the digest was otherwise valid), the DigestAuthenticationEntryPoint will send a "stale=true" header.
This tells the user agent there is no need to disturb the user (as the password and username etc is correct), but simply to try again using a new nonce.

An appropriate value for the nonceValiditySeconds parameter of DigestAuthenticationEntryPoint depends on your application.
Extremely secure applications should note that an intercepted authentication header can be used to impersonate the principal until the expirationTime contained in the nonce is reached.
This is the key principle when selecting an appropriate setting, but it would be unusual for immensely secure applications to not be running over TLS/HTTPS in the first instance.

Because of the more complex implementation of Digest Authentication, there are often user agent issues.
For example, Internet Explorer fails to present an “opaque” token on subsequent requests in the same session.
Spring Security filters therefore encapsulate all state information into the “nonce” token instead.
In our testing, Spring Security’s implementation works reliably with Mozilla Firefox and Internet Explorer, correctly handling nonce timeouts etc.

Configuration

Now that we’ve reviewed the theory, let’s see how to use it.
To implement HTTP Digest Authentication, it is necessary to define DigestAuthenticationFilter in the filter chain.
The application context will need to define the DigestAuthenticationFilter and its required collaborators:

The configured UserDetailsService is needed because DigestAuthenticationFilter must have direct access to the clear text password of a user.
Digest Authentication will NOT work if you are using encoded passwords in your DAO [15].
The DAO collaborator, along with the UserCache, are typically shared directly with a DaoAuthenticationProvider.
The authenticationEntryPoint property must be DigestAuthenticationEntryPoint, so that DigestAuthenticationFilter can obtain the correct realmName and key for digest calculations.

Like BasicAuthenticationFilter, if authentication is successful an Authentication request token will be placed into the SecurityContextHolder.
If the authentication event was successful, or authentication was not attempted because the HTTP header did not contain a Digest Authentication request, the filter chain will continue as normal.
The only time the filter chain will be interrupted is if authentication fails and the AuthenticationEntryPoint is called, as discussed in the previous paragraph.

Digest Authentication’s RFC offers a range of additional features to further increase security.
For example, the nonce can be changed on every request.
Despite this, Spring Security implementation was designed to minimise the complexity of the implementation (and the doubtless user agent incompatibilities that would emerge), and avoid needing to store server-side state.
You are invited to review RFC 2617 if you wish to explore these features in more detail.
As far as we are aware, Spring Security’s implementation does comply with the minimum standards of this RFC.

10.5 Remember-Me Authentication

10.5.1 Overview

Remember-me or persistent-login authentication refers to web sites being able to remember the identity of a principal between sessions.
This is typically accomplished by sending a cookie to the browser, with the cookie being detected during future sessions and causing automated login to take place.
Spring Security provides the necessary hooks for these operations to take place, and has two concrete remember-me implementations.
One uses hashing to preserve the security of cookie-based tokens and the other uses a database or other persistent storage mechanism to store the generated tokens.

Note that both implementations require a UserDetailsService.
If you are using an authentication provider which doesn’t use a UserDetailsService (for example, the LDAP provider) then it won’t work unless you also have a UserDetailsService bean in your application context.

10.5.2 Simple Hash-Based Token Approach

This approach uses hashing to achieve a useful remember-me strategy.
In essence a cookie is sent to the browser upon successful interactive authentication, with the cookie being composed as follows:

base64(username + ":" + expirationTime + ":" +
md5Hex(username + ":" + expirationTime + ":" password + ":" + key))
username: As identifiable to the UserDetailsService
password: That matches the one in the retrieved UserDetails
expirationTime: The date and time when the remember-me token expires, expressed in milliseconds
key: A private key to prevent modification of the remember-me token

As such the remember-me token is valid only for the period specified, and provided that the username, password and key does not change.
Notably, this has a potential security issue in that a captured remember-me token will be usable from any user agent until such time as the token expires.
This is the same issue as with digest authentication.
If a principal is aware a token has been captured, they can easily change their password and immediately invalidate all remember-me tokens on issue.
If more significant security is needed you should use the approach described in the next section.
Alternatively remember-me services should simply not be used at all.

If you are familiar with the topics discussed in the chapter on namespace configuration, you can enable remember-me authentication just by adding the <remember-me> element:

<http>
...
<remember-mekey="myAppKey"/></http>

The UserDetailsService will normally be selected automatically.
If you have more than one in your application context, you need to specify which one should be used with the user-service-ref attribute, where the value is the name of your UserDetailsService bean.

10.5.4 Remember-Me Interfaces and Implementations

Remember-me is used with UsernamePasswordAuthenticationFilter, and is implemented via hooks in the AbstractAuthenticationProcessingFilter superclass.
It is also used within BasicAuthenticationFilter.
The hooks will invoke a concrete RememberMeServices at the appropriate times.
The interface looks like this:

Please refer to the Javadoc for a fuller discussion on what the methods do, although note at this stage that AbstractAuthenticationProcessingFilter only calls the loginFail() and loginSuccess() methods.
The autoLogin() method is called by RememberMeAuthenticationFilter whenever the SecurityContextHolder does not contain an Authentication.
This interface therefore provides the underlying remember-me implementation with sufficient notification of authentication-related events, and delegates to the implementation whenever a candidate web request might contain a cookie and wish to be remembered.
This design allows any number of remember-me implementation strategies.
We’ve seen above that Spring Security provides two implementations.
We’ll look at these in turn.

TokenBasedRememberMeServices

This implementation supports the simpler approach described in Section 10.5.2, “Simple Hash-Based Token Approach”.
TokenBasedRememberMeServices generates a RememberMeAuthenticationToken, which is processed by RememberMeAuthenticationProvider.
A key is shared between this authentication provider and the TokenBasedRememberMeServices.
In addition, TokenBasedRememberMeServices requires A UserDetailsService from which it can retrieve the username and password for signature comparison purposes, and generate the RememberMeAuthenticationToken to contain the correct GrantedAuthority s.
Some sort of logout command should be provided by the application that invalidates the cookie if the user requests this.
TokenBasedRememberMeServices also implements Spring Security’s LogoutHandler interface so can be used with LogoutFilter to have the cookie cleared automatically.

The beans required in an application context to enable remember-me services are as follows:

PersistentTokenBasedRememberMeServices

This class can be used in the same way as TokenBasedRememberMeServices, but it additionally needs to be configured with a PersistentTokenRepository to store the tokens.
There are two standard implementations.

You like to win money, so you click on the submit button.
In the process, you have unintentionally transferred $100 to a malicious user.
This happens because, while the evil website cannot see your cookies, the cookies associated with your bank are still sent along with the request.

Worst yet, this whole process could have been automated using JavaScript.
This means you didn’t even need to click on the button.
So how do we protect ourselves from such attacks?

10.6.2 Synchronizer Token Pattern

The issue is that the HTTP request from the bank’s website and the request from the evil website are exactly the same.
This means there is no way to reject requests coming from the evil website and allow requests coming from the bank’s website.
To protect against CSRF attacks we need to ensure there is something in the request that the evil site is unable to provide.

One solution is to use the Synchronizer Token Pattern.
This solution is to ensure that each request requires, in addition to our session cookie, a randomly generated token as an HTTP parameter.
When a request is submitted, the server must look up the expected value for the parameter and compare it against the actual value in the request.
If the values do not match, the request should fail.

We can relax the expectations to only require the token for each HTTP request that updates state.
This can be safely done since the same origin policy ensures the evil site cannot read the response.
Additionally, we do not want to include the random token in HTTP GET as this can cause the tokens to be leaked.

Let’s take a look at how our example would change.
Assume the randomly generated token is present in an HTTP parameter named _csrf.
For example, the request to transfer money would look like this:

You will notice that we added the _csrf parameter with a random value.
Now the evil website will not be able to guess the correct value for the _csrf parameter (which must be explicitly provided on the evil website) and the transfer will fail when the server compares the actual token to the expected token.

10.6.3 When to use CSRF protection

When should you use CSRF protection? Our recommendation is to use CSRF protection for any request that could be processed by a browser by normal users.
If you are only creating a service that is used by non-browser clients, you will likely want to disable CSRF protection.

CSRF protection and JSON

A common question is "do I need to protect JSON requests made by javascript?" The short answer is, it depends.
However, you must be very careful as there are CSRF exploits that can impact JSON requests.
For example, a malicious user can create a CSRF with JSON using the following form:

If an application were not validating the Content-Type, then it would be exposed to this exploit.
Depending on the setup, a Spring MVC application that validates the Content-Type could still be exploited by updating the URL suffix to end with ".json" as shown below:

CSRF and Stateless Browser Applications

What if my application is stateless? That doesn’t necessarily mean you are protected.
In fact, if a user does not need to perform any actions in the web browser for a given request, they are likely still vulnerable to CSRF attacks.

For example, consider an application uses a custom cookie that contains all the state within it for authentication instead of the JSESSIONID.
When the CSRF attack is made the custom cookie will be sent with the request in the same manner that the JSESSIONID cookie was sent in our previous example.

Users using basic authentication are also vulnerable to CSRF attacks since the browser will automatically include the username password in any requests in the same manner that the JSESSIONID cookie was sent in our previous example.

10.6.4 Using Spring Security CSRF Protection

So what are the steps necessary to use Spring Security’s to protect our site against CSRF attacks? The steps to using Spring Security’s CSRF protection are outlined below:

Use proper HTTP verbs

The first step to protecting against CSRF attacks is to ensure your website uses proper HTTP verbs.
Specifically, before Spring Security’s CSRF support can be of use, you need to be certain that your application is using PATCH, POST, PUT, and/or DELETE for anything that modifies state.

This is not a limitation of Spring Security’s support, but instead a general requirement for proper CSRF prevention.
The reason is that including private information in an HTTP GET can cause the information to be leaked.
See RFC 2616 Section 15.1.3 Encoding Sensitive Information in URI’s for general guidance on using POST instead of GET for sensitive information.

Configure CSRF Protection

The next step is to include Spring Security’s CSRF protection within your application.
Some frameworks handle invalid CSRF tokens by invaliding the user’s session, but this causes its own problems.
Instead by default Spring Security’s CSRF protection will produce an HTTP 403 access denied.
This can be customized by configuring the AccessDeniedHandler to process InvalidCsrfTokenException differently.

As of Spring Security 4.0, CSRF protection is enabled by default with XML configuration.
If you would like to disable CSRF protection, the corresponding XML configuration can be seen below.

<http><!-- ... --><csrfdisabled="true"/></http>

CSRF protection is enabled by default with Java Configuration.
If you would like to disable CSRF, the corresponding Java configuration can be seen below.
Refer to the Javadoc of csrf() for additional customizations in how CSRF protection is configured.

Include the CSRF Token

Form Submissions

The last step is to ensure that you include the CSRF token in all PATCH, POST, PUT, and DELETE methods.
One way to approach this is to use the _csrf request attribute to obtain the current CsrfToken.
An example of doing this with a JSP is shown below:

An easier approach is to use the csrfInput tag from the Spring Security JSP tag library.

Note

If you are using Spring MVC <form:form> tag or Thymeleaf 2.1+ and are using @EnableWebSecurity, the CsrfToken is automatically included for you (using the CsrfRequestDataValueProcessor).

Ajax and JSON Requests

If you are using JSON, then it is not possible to submit the CSRF token within an HTTP parameter.
Instead you can submit the token within a HTTP header.
A typical pattern would be to include the CSRF token within your meta tags.
An example with a JSP is shown below:

As an alternative to jQuery, we recommend using cujoJS’s rest.js.
The rest.js module provides advanced support for working with HTTP requests and responses in RESTful ways.
A core capability is the ability to contextualize the HTTP client adding behavior as needed by chaining interceptors on to the client.

The configured client can be shared with any component of the application that needs to make a request to the CSRF protected resource.
One significant difference between rest.js and jQuery is that only requests made with the configured client will contain the CSRF token, vs jQuery where all requests will include the token.
The ability to scope which requests receive the token helps guard against leaking the CSRF token to a third party.
Please refer to the rest.js reference documentation for more information on rest.js.

CookieCsrfTokenRepository

There can be cases where users will want to persist the CsrfToken in a cookie.
By default the CookieCsrfTokenRepository will write to a cookie named XSRF-TOKEN and read it from a header named X-XSRF-TOKEN or the HTTP parameter _csrf.
These defaults come from AngularJS

You can configure CookieCsrfTokenRepository in XML using the following:

The sample explicitly sets cookieHttpOnly=false.
This is necessary to allow JavaScript (i.e. AngularJS) to read it.
If you do not need the ability to read the cookie with JavaScript directly, it is recommended to omit cookieHttpOnly=false to improve security.

You can configure CookieCsrfTokenRepository in Java Configuration using:

The sample explicitly sets cookieHttpOnly=false.
This is necessary to allow JavaScript (i.e. AngularJS) to read it.
If you do not need the ability to read the cookie with JavaScript directly, it is recommended to omit cookieHttpOnly=false (by using new CookieCsrfTokenRepository() instead) to improve security.

10.6.5 CSRF Caveats

There are a few caveats when implementing CSRF.

Timeouts

One issue is that the expected CSRF token is stored in the HttpSession, so as soon as the HttpSession expires your configured AccessDeniedHandler will receive a InvalidCsrfTokenException.
If you are using the default AccessDeniedHandler, the browser will get an HTTP 403 and display a poor error message.

Note

One might ask why the expected CsrfToken isn’t stored in a cookie by default.
This is because there are known exploits in which headers (i.e. specify the cookies) can be set by another domain.
This is the same reason Ruby on Rails no longer skips CSRF checks when the header X-Requested-With is present.
See this webappsec.org thread for details on how to perform the exploit.
Another disadvantage is that by removing the state (i.e. the timeout) you lose the ability to forcibly terminate the token if it is compromised.

A simple way to mitigate an active user experiencing a timeout is to have some JavaScript that lets the user know their session is about to expire.
The user can click a button to continue and refresh the session.

Alternatively, specifying a custom AccessDeniedHandler allows you to process the InvalidCsrfTokenException any way you like.
For an example of how to customize the AccessDeniedHandler refer to the provided links for both xml and Java configuration.

Finally, the application can be configured to use CookieCsrfTokenRepository which will not expire.
As previously mentioned, this is not as secure as using a session, but in many cases can be good enough.

Logging In

In order to protect against forging log in requests the log in form should be protected against CSRF attacks too.
Since the CsrfToken is stored in HttpSession, this means an HttpSession will be created as soon as CsrfToken token attribute is accessed.
While this sounds bad in a RESTful / stateless architecture the reality is that state is necessary to implement practical security.
Without state, we have nothing we can do if a token is compromised.
Practically speaking, the CSRF token is quite small in size and should have a negligible impact on our architecture.

A common technique to protect the log in form is by using a JavaScript function to obtain a valid CSRF token before the form submission.
By doing this, there is no need to think about session timeouts (discussed in the previous section) because the session is created right before the form submission (assuming that CookieCsrfTokenRepository isn’t configured instead), so the user can stay on the login page and submit the username/password when he wants.
In order to achieve this, you can take advantage of the CsrfTokenArgumentResolver provided by Spring Security and expose an endpoint like it’s described on here.

Logging Out

Adding CSRF will update the LogoutFilter to only use HTTP POST.
This ensures that log out requires a CSRF token and that a malicious user cannot forcibly log out your users.

One approach is to use a form for log out.
If you really want a link, you can use JavaScript to have the link perform a POST (i.e. maybe on a hidden form).
For browsers with JavaScript that is disabled, you can optionally have the link take the user to a log out confirmation page that will perform the POST.

If you really want to use HTTP GET with logout you can do so, but remember this is generally not recommended.
For example, the following Java Configuration will perform logout with the URL /logout is requested with any HTTP method:

Placing MultipartFilter before Spring Security

The first option is to ensure that the MultipartFilter is specified before the Spring Security filter.
Specifying the MultipartFilter before the Spring Security filter means that there is no authorization for invoking the MultipartFilter which means anyone can place temporary files on your server.
However, only authorized users will be able to submit a File that is processed by your application.
In general, this is the recommended approach because the temporary file upload should have a negligble impact on most servers.

To ensure MultipartFilter is specified before the Spring Security filter with java configuration, users can override beforeSpringSecurityFilterChain as shown below:

To ensure MultipartFilter is specified before the Spring Security filter with XML configuration, users can ensure the <filter-mapping> element of the MultipartFilter is placed before the springSecurityFilterChain within the web.xml as shown below:

Include CSRF token in action

If allowing unauthorized users to upload temporariy files is not acceptable, an alternative is to place the MultipartFilter after the Spring Security filter and include the CSRF as a query parameter in the action attribute of the form.
An example with a jsp is shown below

HiddenHttpMethodFilter

The HiddenHttpMethodFilter should be placed before the Spring Security filter.
In general this is true, but it could have additional implications when protecting against CSRF attacks.

Note that the HiddenHttpMethodFilter only overrides the HTTP method on a POST, so this is actually unlikely to cause any real problems.
However, it is still best practice to ensure it is placed before Spring Security’s filters.

10.6.6 Overriding Defaults

Spring Security’s goal is to provide defaults that protect your users from exploits.
This does not mean that you are forced to accept all of its defaults.

For example, you can provide a custom CsrfTokenRepository to override the way in which the CsrfToken is stored.

You can also specify a custom RequestMatcher to determine which requests are protected by CSRF (i.e. perhaps you don’t care if log out is exploited).
In short, if Spring Security’s CSRF protection doesn’t behave exactly as you want it, you are able to customize the behavior.
Refer to the the section called “<csrf>” documentation for details on how to make these customizations with XML and the CsrfConfigurer javadoc for details on how to make these customizations when using Java configuration.

10.7 CORS

Spring Framework provides first class support for CORS.
CORS must be processed before Spring Security because the pre-flight request will not contain any cookies (i.e. the JSESSIONID).
If the request does not contain any cookies and Spring Security is first, the request will determine the user is not authenticated (since there are no cookies in the request) and reject it.

The easiest way to ensure that CORS is handled first is to use the CorsFilter.
Users can integrate the CorsFilter with Spring Security by providing a CorsConfigurationSource using the following:

If necessary, you can disable all of the HTTP Security response headers with the following XML configuration below:

<http><!-- ... --><headersdisabled="true" /></http>

Cache Control

In the past Spring Security required you to provide your own cache control for your web application.
This seemed reasonable at the time, but browser caches have evolved to include caches for secure connections as well.
This means that a user may view an authenticated page, log out, and then a malicious user can use the browser history to view the cached page.
To help mitigate this Spring Security has added cache control support which will insert the following headers into you response.

Simply adding the <headers> element with no child elements will automatically add Cache Control and quite a few other protections.
However, if you only want cache control, you can enable this feature using Spring Security’s XML namespace with the <cache-control> element and the [email protected] attribute.

If you actually want to cache specific responses, your application can selectively invoke HttpServletResponse.setHeader(String,String) to override the header set by Spring Security.
This is useful to ensure things like CSS, JavaScript, and images are properly cached.

When using Spring Web MVC, this is typically done within your configuration.
For example, the following configuration will ensure that the cache headers are set for all of your resources:

Content Type Options

Historically browsers, including Internet Explorer, would try to guess the content type of a request using content sniffing.
This allowed browsers to improve the user experience by guessing the content type on resources that had not specified the content type.
For example, if a browser encountered a JavaScript file that did not have the content type specified, it would be able to guess the content type and then execute it.

Note

There are many additional things one should do (i.e. only display the document in a distinct domain, ensure Content-Type header is set, sanitize the document, etc) when allowing content to be uploaded.
However, these measures are out of the scope of what Spring Security provides.
It is also important to point out when disabling content sniffing, you must specify the content type in order for things to work properly.

The problem with content sniffing is that this allowed malicious users to use polyglots (i.e. a file that is valid as multiple content types) to execute XSS attacks.
For example, some sites may allow users to submit a valid postscript document to a website and view it.
A malicious user might create a postscript document that is also a valid JavaScript file and execute a XSS attack with it.

Content sniffing can be disabled by adding the following header to our response:

X-Content-Type-Options: nosniff

Just as with the cache control element, the nosniff directive is added by default when using the <headers> element with no child elements.
However, if you want more control over which headers are added you can use the <content-type-options> element and the [email protected] attribute as shown below:

The X-Content-Type-Options header is added by default with Spring Security Java configuration.
If you want more control over the headers, you can explicitly specify the content type options with the following:

In accordance with RFC6797, the HSTS header is only injected into HTTPS responses.
In order for the browser to acknowledge the header, the browser must first trust the CA that signed the SSL certificate used to make the connection (not just the SSL certificate).

One way for a site to be marked as a HSTS host is to have the host preloaded into the browser.
Another is to add the "Strict-Transport-Security" header to the response.
For example the following would instruct the browser to treat the domain as an HSTS host for a year (there are approximately 31536000 seconds in a year):

Strict-Transport-Security: max-age=31536000 ; includeSubDomains

The optional includeSubDomains directive instructs Spring Security that subdomains (i.e. secure.mybank.example.com) should also be treated as an HSTS domain.

As with the other headers, Spring Security adds HSTS by default.
You can customize HSTS headers with the <hsts> element as shown below:

HTTP Public Key Pinning (HPKP)

HTTP Public Key Pinning (HPKP) is a security feature that tells a web client to associate a specific cryptographic public key with a certain web server to prevent Man in the Middle (MITM) attacks with forged certificates.

To ensure the authenticity of a server’s public key used in TLS sessions, this public key is wrapped into a X.509 certificate which is usually signed by a certificate authority (CA).
Web clients such as browsers trust a lot of these CAs, which can all create certificates for arbitrary domain names.
If an attacker is able to compromise a single CA, they can perform MITM attacks on various TLS connections.
HPKP can circumvent this threat for the HTTPS protocol by telling the client which public key belongs to a certain web server.
HPKP is a Trust on First Use (TOFU) technique.
The first time a web server tells a client via a special HTTP header which public keys belong to it, the client stores this information for a given period of time.
When the client visits the server again, it expects a certificate containing a public key whose fingerprint is already known via HPKP.
If the server delivers an unknown public key, the client should present a warning to the user.

Note

Because the user-agent needs to validate the pins against the SSL certificate chain, the HPKP header is only injected into HTTPS responses.

Enabling this feature for your site is as simple as returning the Public-Key-Pins HTTP header when your site is accessed over HTTPS.
For example, the following would instruct the user-agent to only report pin validation failures to a given URI (via the report-uri directive) for 2 pins:

X-Frame-Options

Allowing your website to be added to a frame can be a security issue.
For example, using clever CSS styling users could be tricked into clicking on something that they were not intending (video demo).
For example, a user that is logged into their bank might click a button that grants access to other users.
This sort of attack is known as Clickjacking.

There are a number ways to mitigate clickjacking attacks.
For example, to protect legacy browsers from clickjacking attacks you can use frame breaking code.
While not perfect, the frame breaking code is the best you can do for the legacy browsers.

A more modern approach to address clickjacking is to use X-Frame-Options header:

X-Frame-Options: DENY

The X-Frame-Options response header instructs the browser to prevent any site with this header in the response from being rendered within a frame.
By default, Spring Security disables rendering within an iframe.

You can customize X-Frame-Options with the frame-options element.
For example, the following will instruct Spring Security to use "X-Frame-Options: SAMEORIGIN" which allows iframes within the same domain:

X-XSS-Protection

Some browsers have built in support for filtering out reflected XSS attacks.
This is by no means foolproof, but does assist in XSS protection.

The filtering is typically enabled by default, so adding the header typically just ensures it is enabled and instructs the browser what to do when a XSS attack is detected.
For example, the filter might try to change the content in the least invasive way to still render everything.
At times, this type of replacement can become a XSS vulnerability in itself.
Instead, it is best to block the content rather than attempt to fix it.
To do this we can add the following header:

X-XSS-Protection: 1; mode=block

This header is included by default.
However, we can customize it if we wanted.
For example:

Content Security Policy (CSP)

Content Security Policy (CSP) is a mechanism that web applications can leverage to mitigate content injection vulnerabilities, such as cross-site scripting (XSS).
CSP is a declarative policy that provides a facility for web application authors to declare and ultimately inform the client (user-agent) about the sources from which the web application expects to load resources.

Note

Content Security Policy is not intended to solve all content injection vulnerabilities.
Instead, CSP can be leveraged to help reduce the harm caused by content injection attacks.
As a first line of defense, web application authors should validate their input and encode their output.

A web application may employ the use of CSP by including one of the following HTTP headers in the response:

Content-Security-Policy

Content-Security-Policy-Report-Only

Each of these headers are used as a mechanism to deliver a security policy to the client.
A security policy contains a set of security policy directives (for example, script-src and object-src), each responsible for declaring the restrictions for a particular resource representation.

For example, a web application can declare that it expects to load scripts from specific, trusted sources, by including the following header in the response:

An attempt to load a script from another source other than what is declared in the script-src directive will be blocked by the user-agent.
Additionally, if the report-uri directive is declared in the security policy, then the violation will be reported by the user-agent to the declared URL.

For example, if a web application violates the declared security policy, the following response header will instruct the user-agent to send violation reports to the URL specified in the policy’s report-uri directive.

Violation reports are standard JSON structures that can be captured either by the web application’s own API or by a publicly hosted CSP violation reporting service, such as, REPORT-URI.

The Content-Security-Policy-Report-Only header provides the capability for web application authors and administrators to monitor security policies, rather than enforce them.
This header is typically used when experimenting and/or developing security policies for a site.
When a policy is deemed effective, it can be enforced by using the Content-Security-Policy header field instead.

Given the following response header, the policy declares that scripts may be loaded from one of two possible sources.

If the site violates this policy, by attempting to load a script from evil.com, the user-agent will send a violation report to the declared URL specified by the report-uri directive, but still allow the violating resource to load nevertheless.

Configuring Content Security Policy

It’s important to note that Spring Security does not add Content Security Policy by default.
The web application author must declare the security policy(s) to enforce and/or monitor for the protected resources.

Additional Resources

Applying Content Security Policy to a web application is often a non-trivial undertaking.
The following resources may provide further assistance in developing effective security policies for your site.

Feature Policy

Feature Policy is a mechanism that allows web developers to selectively enable, disable, and modify the behavior of certain APIs and web features in the browser.

Feature-Policy: geolocation 'self'

With Feature Policy, developers can opt-in to a set of "policies" for the browser to enforce on specific features used throughout your site.
These policies restrict what APIs the site can access or modify the browser’s default behavior for certain features.

Configuring Feature Policy

Spring Security doesn’t add Feature Policy header by default.

You can enable the Feature-Policy header using XML configuration with the <feature-policy> element as shown below:

Headers Writer

When the namespace or Java configuration does not support the headers you want, you can create a custom HeadersWriter instance or even provide a custom implementation of the HeadersWriter.

Let’s take a look at an example of using an custom instance of XFrameOptionsHeaderWriter.
Perhaps you want to allow framing of content for the same origin.
This is easily supported by setting the policy attribute to "SAMEORIGIN", but let’s take a look at a more explicit example using the ref attribute.

DelegatingRequestMatcherHeaderWriter

At times you may want to only write a header for certain requests.
For example, perhaps you want to only protect your log in page from being framed.
You could use the DelegatingRequestMatcherHeaderWriter to do so.
When using the XML namespace configuration, this can be done with the following:

10.9 Session Management

HTTP session related functionality is handled by a combination of the SessionManagementFilter and the SessionAuthenticationStrategy interface, which the filter delegates to.
Typical usage includes session-fixation protection attack prevention, detection of session timeouts and restrictions on how many sessions an authenticated user may have open concurrently.

10.9.1 SessionManagementFilter

The SessionManagementFilter checks the contents of the SecurityContextRepository against the current contents of the SecurityContextHolder to determine whether a user has been authenticated during the current request, typically by a non-interactive authentication mechanism, such as pre-authentication or remember-me [17].
If the repository contains a security context, the filter does nothing.
If it doesn’t, and the thread-local SecurityContext contains a (non-anonymous) Authentication object, the filter assumes they have been authenticated by a previous filter in the stack.
It will then invoke the configured SessionAuthenticationStrategy.

If the user is not currently authenticated, the filter will check whether an invalid session ID has been requested (because of a timeout, for example) and will invoke the configured InvalidSessionStrategy, if one is set.
The most common behaviour is just to redirect to a fixed URL and this is encapsulated in the standard implementation SimpleRedirectInvalidSessionStrategy.
The latter is also used when configuring an invalid session URL through the namespace,as described earlier.

10.9.2 SessionAuthenticationStrategy

SessionAuthenticationStrategy is used by both SessionManagementFilter and AbstractAuthenticationProcessingFilter, so if you are using a customized form-login class, for example, you will need to inject it into both of these.
In this case, a typical configuration, combining the namespace and custom beans might look like this:

Note that the use of the default, SessionFixationProtectionStrategy may cause issues if you are storing beans in the session which implement HttpSessionBindingListener, including Spring session-scoped beans.
See the Javadoc for this class for more information.

10.9.3 Concurrency Control

Spring Security is able to prevent a principal from concurrently authenticating to the same application more than a specified number of times.
Many ISVs take advantage of this to enforce licensing, whilst network administrators like this feature because it helps prevent people from sharing login names.
You can, for example, stop user "Batman" from logging onto the web application from two different sessions.
You can either expire their previous login or you can report an error when they try to log in again, preventing the second login.
Note that if you are using the second approach, a user who has not explicitly logged out (but who has just closed their browser, for example) will not be able to log in again until their original session expires.

Concurrency control is supported by the namespace, so please check the earlier namespace chapter for the simplest configuration.
Sometimes you need to customize things though.

The implementation uses a specialized version of SessionAuthenticationStrategy, called ConcurrentSessionControlAuthenticationStrategy.

Note

Previously the concurrent authentication check was made by the ProviderManager, which could be injected with a ConcurrentSessionController.
The latter would check if the user was attempting to exceed the number of permitted sessions.
However, this approach required that an HTTP session be created in advance, which is undesirable.
In Spring Security 3, the user is first authenticated by the AuthenticationManager and once they are successfully authenticated, a session is created and the check is made whether they are allowed to have another session open.

To use concurrent session support, you’ll need to add the following to web.xml:

In addition, you will need to add the ConcurrentSessionFilter to your FilterChainProxy.
The ConcurrentSessionFilter requires two constructor arguments, sessionRegistry, which generally points to an instance of SessionRegistryImpl, and sessionInformationExpiredStrategy, which defines the strategy to apply when a session has expired.
A configuration using the namespace to create the FilterChainProxy and other default beans might look like this:

Adding the listener to web.xml causes an ApplicationEvent to be published to the Spring ApplicationContext every time a HttpSession commences or terminates.
This is critical, as it allows the SessionRegistryImpl to be notified when a session ends.
Without it, a user will never be able to log back in again once they have exceeded their session allowance, even if they log out of another session or it times out.

Querying the SessionRegistry for currently authenticated users and their sessions

Setting up concurrency-control, either through the namespace or using plain beans has the useful side effect of providing you with a reference to the SessionRegistry which you can use directly within your application, so even if you don’t want to restrict the number of sessions a user may have, it may be worth setting up the infrastructure anyway.
You can set the maximumSession property to -1 to allow unlimited sessions.
If you’re using the namespace, you can set an alias for the internally-created SessionRegistry using the session-registry-alias attribute, providing a reference which you can inject into your own beans.

The getAllPrincipals() method supplies you with a list of the currently authenticated users.
You can list a user’s sessions by calling the getAllSessions(Object principal, boolean includeExpiredSessions) method, which returns a list of SessionInformation objects.
You can also expire a user’s session by calling expireNow() on a SessionInformation instance.
When the user returns to the application, they will be prevented from proceeding.
You may find these methods useful in an administration application, for example.
Have a look at the Javadoc for more information.

10.10 Anonymous Authentication

10.10.1 Overview

It’s generally considered good security practice to adopt a "deny-by-default" where you explicitly specify what is allowed and disallow everything else.
Defining what is accessible to unauthenticated users is a similar situation, particularly for web applications.
Many sites require that users must be authenticated for anything other than a few URLs (for example the home and login pages).
In this case it is easiest to define access configuration attributes for these specific URLs rather than have for every secured resource.
Put differently, sometimes it is nice to say ROLE_SOMETHING is required by default and only allow certain exceptions to this rule, such as for login, logout and home pages of an application.
You could also omit these pages from the filter chain entirely, thus bypassing the access control checks, but this may be undesirable for other reasons, particularly if the pages behave differently for authenticated users.

This is what we mean by anonymous authentication.
Note that there is no real conceptual difference between a user who is "anonymously authenticated" and an unauthenticated user.
Spring Security’s anonymous authentication just gives you a more convenient way to configure your access-control attributes.
Calls to servlet API calls such as getCallerPrincipal, for example, will still return null even though there is actually an anonymous authentication object in the SecurityContextHolder.

There are other situations where anonymous authentication is useful, such as when an auditing interceptor queries the SecurityContextHolder to identify which principal was responsible for a given operation.
Classes can be authored more robustly if they know the SecurityContextHolder always contains an Authentication object, and never null.

10.10.2 Configuration

Anonymous authentication support is provided automatically when using the HTTP configuration Spring Security 3.0 and can be customized (or disabled) using the <anonymous> element.
You don’t need to configure the beans described here unless you are using traditional bean configuration.

Three classes that together provide the anonymous authentication feature.
AnonymousAuthenticationToken is an implementation of Authentication, and stores the GrantedAuthority s which apply to the anonymous principal.
There is a corresponding AnonymousAuthenticationProvider, which is chained into the ProviderManager so that AnonymousAuthenticationToken s are accepted.
Finally, there is an AnonymousAuthenticationFilter, which is chained after the normal authentication mechanisms and automatically adds an AnonymousAuthenticationToken to the SecurityContextHolder if there is no existing Authentication held there.
The definition of the filter and authentication provider appears as follows:

The key is shared between the filter and authentication provider, so that tokens created by the former are accepted by the latter [18].
The userAttribute is expressed in the form of usernameInTheAuthenticationToken,grantedAuthority[,grantedAuthority].
This is the same syntax as used after the equals sign for the userMap property of InMemoryDaoImpl.

As explained earlier, the benefit of anonymous authentication is that all URI patterns can have security applied to them.
For example:

10.10.3 AuthenticationTrustResolver

Rounding out the anonymous authentication discussion is the AuthenticationTrustResolver interface, with its corresponding AuthenticationTrustResolverImpl implementation.
This interface provides an isAnonymous(Authentication) method, which allows interested classes to take into account this special type of authentication status.
The ExceptionTranslationFilter uses this interface in processing AccessDeniedException s.
If an AccessDeniedException is thrown, and the authentication is of an anonymous type, instead of throwing a 403 (forbidden) response, the filter will instead commence the AuthenticationEntryPoint so the principal can authenticate properly.
This is a necessary distinction, otherwise principals would always be deemed "authenticated" and never be given an opportunity to login via form, basic, digest or some other normal authentication mechanism.

You will often see the ROLE_ANONYMOUS attribute in the above interceptor configuration replaced with IS_AUTHENTICATED_ANONYMOUSLY, which is effectively the same thing when defining access controls.
This is an example of the use of the AuthenticatedVoter which we will see in the authorization chapter.
It uses an AuthenticationTrustResolver to process this particular configuration attribute and grant access to anonymous users.
The AuthenticatedVoter approach is more powerful, since it allows you to differentiate between anonymous, remember-me and fully-authenticated users.
If you don’t need this functionality though, then you can stick with ROLE_ANONYMOUS, which will be processed by Spring Security’s standard RoleVoter.

10.11 WebSocket Security

Spring Security 4 added support for securing Spring’s WebSocket support.
This section describes how to use Spring Security’s WebSocket support.

Spring Security does not provide direct JSR-356 support because doing so would provide little value.
This is because the format is unknown, so there is little Spring can do to secure an unknown format.
Additionally, JSR-356 does not provide a way to intercept messages, so security would be rather invasive.

10.11.1 WebSocket Configuration

Spring Security 4.0 has introduced authorization support for WebSockets through the Spring Messaging abstraction.
To configure authorization using Java Configuration, simply extend the AbstractSecurityWebSocketMessageBrokerConfigurer and configure the MessageSecurityMetadataSourceRegistry.
For example:

The SecurityContextHolder is populated with the user within the simpUser header attribute for any inbound request.

Our messages require the proper authorization. Specifically, any inbound message that starts with "/user/" will require ROLE_USER. Additional details on authorization can be found in Section 10.11.3, “WebSocket Authorization”

Spring Security also provides XML Namespace support for securing WebSockets.
A comparable XML based configuration looks like the following:

The SecurityContextHolder is populated with the user within the simpUser header attribute for any inbound request.

Our messages require the proper authorization. Specifically, any inbound message that starts with "/user/" will require ROLE_USER. Additional details on authorization can be found in Section 10.11.3, “WebSocket Authorization”

10.11.2 WebSocket Authentication

WebSockets reuse the same authentication information that is found in the HTTP request when the WebSocket connection was made.
This means that the Principal on the HttpServletRequest will be handed off to WebSockets.
If you are using Spring Security, the Principal on the HttpServletRequest is overridden automatically.

More concretely, to ensure a user has authenticated to your WebSocket application, all that is necessary is to ensure that you setup Spring Security to authenticate your HTTP based web application.

10.11.3 WebSocket Authorization

Spring Security 4.0 has introduced authorization support for WebSockets through the Spring Messaging abstraction.
To configure authorization using Java Configuration, simply extend the AbstractSecurityWebSocketMessageBrokerConfigurer and configure the MessageSecurityMetadataSourceRegistry.
For example:

Any message of type CONNECT, UNSUBSCRIBE, or DISCONNECT will require the user to be authenticated

Anyone can subscribe to /user/queue/errors

Any message that has a destination starting with "/app/" will be require the user to have the role ROLE_USER

Any message that starts with "/user/" or "/topic/friends/" that is of type SUBSCRIBE will require ROLE_USER

Any other message of type MESSAGE or SUBSCRIBE is rejected. Due to 6 we do not need this step, but it illustrates how one can match on specific message types.

Any other message with a destination is rejected. This is a good idea to ensure that you do not miss any messages.

WebSocket Authorization Notes

In order to properly secure your application it is important to understand Spring’s WebSocket support.

WebSocket Authorization on Message Types

It is important to understand the distinction between SUBSCRIBE and MESSAGE types of messages and how it works within Spring.

Consider a chat application.

The system can send notifications MESSAGE to all users through a destination of "/topic/system/notifications"

Clients can receive notifications by SUBSCRIBE to the "/topic/system/notifications".

While we want clients to be able to SUBSCRIBE to "/topic/system/notifications", we do not want to enable them to send a MESSAGE to that destination.
If we allowed sending a MESSAGE to "/topic/system/notifications", then clients could send a message directly to that endpoint and impersonate the system.

In general, it is common for applications to deny any MESSAGE sent to a message that starts with the broker prefix (i.e. "/topic/" or "/queue/").

WebSocket Authorization on Destinations

It is also is important to understand how destinations are transformed.

Consider a chat application.

Users can send messages to a specific user by sending a message to the destination of "/app/chat".

The application sees the message, ensures that the "from" attribute is specified as the current user (we cannot trust the client).

The application then sends the message to the recipient using SimpMessageSendingOperations.convertAndSendToUser("toUser", "/queue/messages", message).

The message gets turned into the destination of "/queue/user/messages-<sessionid>"

With the application above, we want to allow our client to listen to "/user/queue" which is transformed into "/queue/user/messages-<sessionid>".
However, we do not want the client to be able to listen to "/queue/*" because that would allow the client to see messages for every user.

In general, it is common for applications to deny any SUBSCRIBE sent to a message that starts with the broker prefix (i.e. "/topic/" or "/queue/").
Of course we may provide exceptions to account for things like

Outbound Messages

Spring contains a section titled Flow of Messages that describes how messages flow through the system.
It is important to note that Spring Security only secures the clientInboundChannel.
Spring Security does not attempt to secure the clientOutboundChannel.

The most important reason for this is performance.
For every message that goes in, there are typically many more that go out.
Instead of securing the outbound messages, we encourage securing the subscription to the endpoints.

10.11.4 Enforcing Same Origin Policy

It is important to emphasize that the browser does not enforce the Same Origin Policy for WebSocket connections.
This is an extremely important consideration.

Why Same Origin?

Consider the following scenario.
A user visits bank.com and authenticates to their account.
The same user opens another tab in their browser and visits evil.com.
The Same Origin Policy ensures that evil.com cannot read or write data to bank.com.

With WebSockets the Same Origin Policy does not apply.
In fact, unless bank.com explicitly forbids it, evil.com can read and write data on behalf of the user.
This means that anything the user can do over the webSocket (i.e. transfer money), evil.com can do on that users behalf.

Since SockJS tries to emulate WebSockets it also bypasses the Same Origin Policy.
This means developers need to explicitly protect their applications from external domains when using SockJS.

Spring WebSocket Allowed Origin

Fortunately, since Spring 4.1.5 Spring’s WebSocket and SockJS support restricts access to the current domain.
Spring Security adds an additional layer of protection to provide defence in depth.

Adding CSRF to Stomp Headers

By default Spring Security requires the CSRF token in any CONNECT message type.
This ensures that only a site that has access to the CSRF token can connect.
Since only the Same Origin can access the CSRF token, external domains are not allowed to make a connection.

Typically we need to include the CSRF token in an HTTP header or an HTTP parameter.
However, SockJS does not allow for these options.
Instead, we must include the token in the Stomp headers

Applications can obtain a CSRF token by accessing the request attribute named _csrf.
For example, the following will allow accessing the CsrfToken in a JSP:

var headerName = "${_csrf.headerName}";
var token = "${_csrf.token}";

If you are using static HTML, you can expose the CsrfToken on a REST endpoint.
For example, the following would expose the CsrfToken on the URL /csrf

10.11.5 Working with SockJS

SockJS provides fallback transports to support older browsers.
When using the fallback options we need to relax a few security constraints to allow SockJS to work with Spring Security.

SockJS & frame-options

SockJS may use an transport that leverages an iframe.
By default Spring Security will deny the site from being framed to prevent Clickjacking attacks.
To allow SockJS frame based transports to work, we need to configure Spring Security to allow the same origin to frame the content.

You can customize X-Frame-Options with the frame-options element.
For example, the following will instruct Spring Security to use "X-Frame-Options: SAMEORIGIN" which allows iframes within the same domain:

SockJS & Relaxing CSRF

SockJS uses a POST on the CONNECT messages for any HTTP based transport.
Typically we need to include the CSRF token in an HTTP header or an HTTP parameter.
However, SockJS does not allow for these options.
Instead, we must include the token in the Stomp headers as described in the section called “Adding CSRF to Stomp Headers”.

It also means we need to relax our CSRF protection with the web layer.
Specifically, we want to disable CSRF protection for our connect URLs.
We do NOT want to disable CSRF protection for every URL.
Otherwise our site will be vulnerable to CSRF attacks.

We can easily achieve this by providing a CSRF RequestMatcher.
Our Java Configuration makes this extremely easy.
For example, if our stomp endpoint is "/chat" we can disable CSRF protection for only URLs that start with "/chat/" using the following configuration:

[6] Note that you’ll need to include the security namespace in your application context XML file in order to use this syntax. The older syntax which used a filter-chain-map is still supported, but is deprecated in favour of the constructor argument injection.

[7] Instead of a path pattern, the request-matcher-ref attribute can be used to specify a RequestMatcher instance for more powerful matching

[8] You have probably seen this when a browser doesn’t support cookies and the jsessionid parameter is appended to the URL after a semi-colon. However the RFC allows the presence of these parameters in any path segment of the URL

[9] The original values will be returned once the request leaves the FilterChainProxy, so will still be available to the application.

[10] So, for example, an original request path /secure;hack=1/somefile.html;hack=2 will be returned as /secure/somefile.html.

[11] We use a forward so that the SecurityContextHolder still contains details of the principal, which may be useful for displaying to the user. In old releases of Spring Security we relied upon the servlet container to handle a 403 error message, which lacked this useful contextual information.

[12] In Spring Security 2.0 and earlier, this filter was called HttpSessionContextIntegrationFilter and performed all the work of storing the context was performed by the filter itself. If you were familiar with this class, then most of the configuration options which were available can now be found on HttpSessionSecurityContextRepository.

[13] For historical reasons, prior to Spring Security 3.0, this filter was called AuthenticationProcessingFilter and the entry point was called AuthenticationProcessingFilterEntryPoint. Since the framework now supports many different forms of authentication, they have both been given more specific names in 3.0.

[14] In versions prior to 3.0, the application flow at this point had evolved to a stage was controlled by a mix of properties on this class and strategy plugins. The decision was made for 3.0 to refactor the code to make these two strategies entirely responsible.

[15] It is possible to encode the password in the format HEX( MD5(username:realm:password) ) provided the DigestAuthenticationFilter.passwordAlreadyEncoded is set to true. However, other password encodings will not work with digest authentication.

[16] Essentially, the username is not included in the cookie, to prevent exposing a valid login name unecessarily. There is a discussion on this in the comments section of this article.

[17] Authentication by mechanisms which perform a redirect after authenticating (such as form-login) will not be detected by SessionManagementFilter, as the filter will not be invoked during the authenticating request. Session-management functionality has to be handled separately in these cases.

[18] The use of the key property should not be regarded as providing any real security here. It is merely a book-keeping exercise. If you are sharing a ProviderManager which contains an AnonymousAuthenticationProvider in a scenario where it is possible for an authenticating client to construct the Authentication object (such as with RMI invocations), then a malicious client could submit an AnonymousAuthenticationToken which it had created itself (with chosen username and authority list). If the key is guessable or can be found out, then the token would be accepted by the anonymous provider. This isn’t a problem with normal usage but if you are using RMI you would be best to use a customized ProviderManager which omits the anonymous provider rather than sharing the one you use for your HTTP authentication mechanisms.

11. Authorization

The advanced authorization capabilities within Spring Security represent one of the most compelling reasons for its popularity.
Irrespective of how you choose to authenticate - whether using a Spring Security-provided mechanism and provider, or integrating with a container or other non-Spring Security authentication authority - you will find the authorization services can be used within your application in a consistent and simple way.

In this part we’ll explore the different AbstractSecurityInterceptor implementations, which were introduced in Part I.
We then move on to explore how to fine-tune authorization through use of domain access control lists.

11.1 Authorization Architecture

11.1.1 Authorities

As we saw in the technical overview, all Authentication implementations store a list of GrantedAuthority objects.
These represent the authorities that have been granted to the principal.
the GrantedAuthority objects are inserted into the Authentication object by the AuthenticationManager and are later read by AccessDecisionManager s when making authorization decisions.

GrantedAuthority is an interface with only one method:

String getAuthority();

This method allows
AccessDecisionManager s to obtain a precise String representation of the GrantedAuthority.
By returning a representation as a String, a GrantedAuthority can be easily "read" by most AccessDecisionManager s.
If a GrantedAuthority cannot be precisely represented as a String, the GrantedAuthority is considered "complex" and getAuthority() must return null.

An example of a "complex" GrantedAuthority would be an implementation that stores a list of operations and authority thresholds that apply to different customer account numbers.
Representing this complex GrantedAuthority as a String would be quite difficult, and as a result the getAuthority() method should return null.
This will indicate to any AccessDecisionManager that it will need to specifically support the GrantedAuthority implementation in order to understand its contents.

Spring Security includes one concrete GrantedAuthority implementation, SimpleGrantedAuthority.
This allows any user-specified String to be converted into a GrantedAuthority.
All AuthenticationProvider s included with the security architecture use SimpleGrantedAuthority to populate the Authentication object.

11.1.2 Pre-Invocation Handling

As we’ve also seen in the Technical Overview chapter, Spring Security provides interceptors which control access to secure objects such as method invocations or web requests.
A pre-invocation decision on whether the invocation is allowed to proceed is made by the AccessDecisionManager.

The AccessDecisionManager

The AccessDecisionManager is called by the AbstractSecurityInterceptor and is responsible for making final access control decisions.
the AccessDecisionManager interface contains three methods:

The AccessDecisionManager's decide method is passed all the relevant information it needs in order to make an authorization decision.
In particular, passing the secure Object enables those arguments contained in the actual secure object invocation to be inspected.
For example, let’s assume the secure object was a MethodInvocation.
It would be easy to query the MethodInvocation for any Customer argument, and then implement some sort of security logic in the AccessDecisionManager to ensure the principal is permitted to operate on that customer.
Implementations are expected to throw an AccessDeniedException if access is denied.

The supports(ConfigAttribute) method is called by the AbstractSecurityInterceptor at startup time to determine if the AccessDecisionManager can process the passed ConfigAttribute.
The supports(Class) method is called by a security interceptor implementation to ensure the configured AccessDecisionManager supports the type of secure object that the security interceptor will present.

Voting-Based AccessDecisionManager Implementations

Whilst users can implement their own AccessDecisionManager to control all aspects of authorization, Spring Security includes several AccessDecisionManager implementations that are based on voting.
Figure 11.1, “Voting Decision Manager” illustrates the relevant classes.

Figure 11.1. Voting Decision Manager

Using this approach, a series of AccessDecisionVoter implementations are polled on an authorization decision.
The AccessDecisionManager then decides whether or not to throw an AccessDeniedException based on its assessment of the votes.

Concrete implementations return an int, with possible values being reflected in the AccessDecisionVoter static fields ACCESS_ABSTAIN, ACCESS_DENIED and ACCESS_GRANTED.
A voting implementation will return ACCESS_ABSTAIN if it has no opinion on an authorization decision.
If it does have an opinion, it must return either ACCESS_DENIED or ACCESS_GRANTED.

There are three concrete AccessDecisionManager s provided with Spring Security that tally the votes.
The ConsensusBased implementation will grant or deny access based on the consensus of non-abstain votes.
Properties are provided to control behavior in the event of an equality of votes or if all votes are abstain.
The AffirmativeBased implementation will grant access if one or more ACCESS_GRANTED votes were received (i.e. a deny vote will be ignored, provided there was at least one grant vote).
Like the ConsensusBased implementation, there is a parameter that controls the behavior if all voters abstain.
The UnanimousBased provider expects unanimous ACCESS_GRANTED votes in order to grant access, ignoring abstains.
It will deny access if there is any ACCESS_DENIED vote.
Like the other implementations, there is a parameter that controls the behaviour if all voters abstain.

It is possible to implement a custom AccessDecisionManager that tallies votes differently.
For example, votes from a particular AccessDecisionVoter might receive additional weighting, whilst a deny vote from a particular voter may have a veto effect.

RoleVoter

The most commonly used AccessDecisionVoter provided with Spring Security is the simple RoleVoter, which treats configuration attributes as simple role names and votes to grant access if the user has been assigned that role.

It will vote if any ConfigAttribute begins with the prefix ROLE_.
It will vote to grant access if there is a GrantedAuthority which returns a String representation (via the getAuthority() method) exactly equal to one or more ConfigAttributes starting with the prefix ROLE_.
If there is no exact match of any ConfigAttribute starting with ROLE_, the RoleVoter will vote to deny access.
If no ConfigAttribute begins with ROLE_, the voter will abstain.

AuthenticatedVoter

Another voter which we’ve implicitly seen is the AuthenticatedVoter, which can be used to differentiate between anonymous, fully-authenticated and remember-me authenticated users.
Many sites allow certain limited access under remember-me authentication, but require a user to confirm their identity by logging in for full access.

When we’ve used the attribute IS_AUTHENTICATED_ANONYMOUSLY to grant anonymous access, this attribute was being processed by the AuthenticatedVoter.
See the Javadoc for this class for more information.

Custom Voters

Obviously, you can also implement a custom AccessDecisionVoter and you can put just about any access-control logic you want in it.
It might be specific to your application (business-logic related) or it might implement some security administration logic.
For example, you’ll find a blog article on the Spring web site which describes how to use a voter to deny access in real-time to users whose accounts have been suspended.

11.1.3 After Invocation Handling

Whilst the AccessDecisionManager is called by the AbstractSecurityInterceptor before proceeding with the secure object invocation, some applications need a way of modifying the object actually returned by the secure object invocation.
Whilst you could easily implement your own AOP concern to achieve this, Spring Security provides a convenient hook that has several concrete implementations that integrate with its ACL capabilities.

Like many other parts of Spring Security, AfterInvocationManager has a single concrete implementation, AfterInvocationProviderManager, which polls a list of AfterInvocationProvider s.
Each AfterInvocationProvider is allowed to modify the return object or throw an AccessDeniedException.
Indeed multiple providers can modify the object, as the result of the previous provider is passed to the next in the list.

Please be aware that if you’re using AfterInvocationManager, you will still need configuration attributes that allow the MethodSecurityInterceptor's AccessDecisionManager to allow an operation.
If you’re using the typical Spring Security included AccessDecisionManager implementations, having no configuration attributes defined for a particular secure method invocation will cause each AccessDecisionVoter to abstain from voting.
In turn, if the AccessDecisionManager property “allowIfAllAbstainDecisions” is false, an AccessDeniedException will be thrown.
You may avoid this potential issue by either (i) setting “allowIfAllAbstainDecisions” to true (although this is generally not recommended) or (ii) simply ensure that there is at least one configuration attribute that an AccessDecisionVoter will vote to grant access for.
This latter (recommended) approach is usually achieved through a ROLE_USER or ROLE_AUTHENTICATED configuration attribute.

11.1.4 Hierarchical Roles

It is a common requirement that a particular role in an application should automatically "include" other roles.
For example, in an application which has the concept of an "admin" and a "user" role, you may want an admin to be able to do everything a normal user can.
To achieve this, you can either make sure that all admin users are also assigned the "user" role.
Alternatively, you can modify every access constraint which requires the "user" role to also include the "admin" role.
This can get quite complicated if you have a lot of different roles in your application.

The use of a role-hierarchy allows you to configure which roles (or authorities) should include others.
An extended version of Spring Security’s RoleVoter, RoleHierarchyVoter, is configured with a RoleHierarchy, from which it obtains all the "reachable authorities" which the user is assigned.
A typical configuration might look like this:

Here we have four roles in a hierarchy ROLE_ADMIN ⇒ ROLE_STAFF ⇒ ROLE_USER ⇒ ROLE_GUEST.
A user who is authenticated with ROLE_ADMIN, will behave as if they have all four roles when security constraints are evaluated against an AccessDecisionManager cconfigured with the above RoleHierarchyVoter.
The > symbol can be thought of as meaning "includes".

Role hierarchies offer a convenient means of simplifying the access-control configuration data for your application and/or reducing the number of authorities which you need to assign to a user.
For more complex requirements you may wish to define a logical mapping between the specific access-rights your application requires and the roles that are assigned to users, translating between the two when loading the user information.

11.2 Secure Object Implementations

11.2.1 AOP Alliance (MethodInvocation) Security Interceptor

Prior to Spring Security 2.0, securing MethodInvocation s needed quite a lot of boiler plate configuration.
Now the recommended approach for method security is to use namespace configuration.
This way the method security infrastructure beans are configured automatically for you so you don’t really need to know about the implementation classes.
We’ll just provide a quick overview of the classes that are involved here.

Method security is enforced using a MethodSecurityInterceptor, which secures MethodInvocation s.
Depending on the configuration approach, an interceptor may be specific to a single bean or shared between multiple beans.
The interceptor uses a MethodSecurityMetadataSource instance to obtain the configuration attributes that apply to a particular method invocation.
MapBasedMethodSecurityMetadataSource is used to store configuration attributes keyed by method names (which can be wildcarded) and will be used internally when the attributes are defined in the application context using the <intercept-methods> or <protect-point> elements.
Other implementations will be used to handle annotation-based configuration.

Explicit MethodSecurityInterceptor Configuration

You can of course configure a MethodSecurityIterceptor directly in your application context for use with one of Spring AOP’s proxying mechanisms:

11.2.2 AspectJ (JoinPoint) Security Interceptor

The AspectJ security interceptor is very similar to the AOP Alliance security interceptor discussed in the previous section.
Indeed we will only discuss the differences in this section.

The AspectJ interceptor is named AspectJSecurityInterceptor.
Unlike the AOP Alliance security interceptor, which relies on the Spring application context to weave in the security interceptor via proxying, the AspectJSecurityInterceptor is weaved in via the AspectJ compiler.
It would not be uncommon to use both types of security interceptors in the same application, with AspectJSecurityInterceptor being used for domain object instance security and the AOP Alliance MethodSecurityInterceptor being used for services layer security.

Let’s first consider how the AspectJSecurityInterceptor is configured in the Spring application context:

As you can see, aside from the class name, the AspectJSecurityInterceptor is exactly the same as the AOP Alliance security interceptor.
Indeed the two interceptors can share the same securityMetadataSource, as the SecurityMetadataSource works with java.lang.reflect.Method s rather than an AOP library-specific class.
Of course, your access decisions have access to the relevant AOP library-specific invocation (ie MethodInvocation or JoinPoint) and as such can consider a range of addition criteria when making access decisions (such as method arguments).

In the above example, the security interceptor will be applied to every instance of PersistableEntity, which is an abstract class not shown (you can use any other class or pointcut expression you like).
For those curious, AspectJCallback is needed because the proceed(); statement has special meaning only within an around() body.
The AspectJSecurityInterceptor calls this anonymous AspectJCallback class when it wants the target object to continue.

You will need to configure Spring to load the aspect and wire it with the AspectJSecurityInterceptor.
A bean declaration which achieves this is shown below:

That’s it!
Now you can create your beans from anywhere within your application, using whatever means you think fit (eg new Person();) and they will have the security interceptor applied.

11.3 Expression-Based Access Control

Spring Security 3.0 introduced the ability to use Spring EL expressions as an authorization mechanism in addition to the simple use of configuration attributes and access-decision voters which have seen before.
Expression-based access control is built on the same architecture but allows complicated Boolean logic to be encapsulated in a single expression.

11.3.1 Overview

Spring Security uses Spring EL for expression support and you should look at how that works if you are interested in understanding the topic in more depth.
Expressions are evaluated with a "root object" as part of the evaluation context.
Spring Security uses specific classes for web and method security as the root object, in order to provide built-in expressions and access to values such as the current principal.

Common Built-In Expressions

The base class for expression root objects is SecurityExpressionRoot.
This provides some common expressions which are available in both web and method security.

Table 11.1. Common built-in expressions

Expression

Description

hasRole([role])

Returns true if the current principal has the specified role.
By default if the supplied role does not start with 'ROLE_' it will be added.
This can be customized by modifying the defaultRolePrefix on DefaultWebSecurityExpressionHandler.

hasAnyRole([role1,role2])

Returns true if the current principal has any of the supplied roles (given as a comma-separated list of strings).
By default if the supplied role does not start with 'ROLE_' it will be added.
This can be customized by modifying the defaultRolePrefix on DefaultWebSecurityExpressionHandler.

hasAuthority([authority])

Returns true if the current principal has the specified authority.

hasAnyAuthority([authority1,authority2])

Returns true if the current principal has any of the supplied authorities (given as a comma-separated list of strings)

principal

Allows direct access to the principal object representing the current user

authentication

Allows direct access to the current Authentication object obtained from the SecurityContext

permitAll

Always evaluates to true

denyAll

Always evaluates to false

isAnonymous()

Returns true if the current principal is an anonymous user

isRememberMe()

Returns true if the current principal is a remember-me user

isAuthenticated()

Returns true if the user is not anonymous

isFullyAuthenticated()

Returns true if the user is not an anonymous or a remember-me user

hasPermission(Object target, Object permission)

Returns true if the user has access to the provided target for the given permission.
For example, hasPermission(domainObject, 'read')

hasPermission(Object targetId, String targetType, Object permission)

Returns true if the user has access to the provided target for the given permission.
For example, hasPermission(1, 'com.example.domain.Message', 'read')

11.3.2 Web Security Expressions

To use expressions to secure individual URLs, you would first need to set the use-expressions attribute in the <http> element to true.
Spring Security will then expect the access attributes of the <intercept-url> elements to contain Spring EL expressions.
The expressions should evaluate to a Boolean, defining whether access should be allowed or not.
For example:

Here we have defined that the "admin" area of an application (defined by the URL pattern) should only be available to users who have the granted authority "admin" and whose IP address matches a local subnet.
We’ve already seen the built-in hasRole expression in the previous section.
The expression hasIpAddress is an additional built-in expression which is specific to web security.
It is defined by the WebSecurityExpressionRoot class, an instance of which is used as the expression root object when evaluation web-access expressions.
This object also directly exposed the HttpServletRequest object under the name request so you can invoke the request directly in an expression.
If expressions are being used, a WebExpressionVoter will be added to the AccessDecisionManager which is used by the namespace.
So if you aren’t using the namespace and want to use expressions, you will have to add one of these to your configuration.

Referring to Beans in Web Security Expressions

If you wish to extend the expressions that are available, you can easily refer to any Spring Bean you expose.
For example, assuming you have a Bean with the name of webSecurity that contains the following method signature:

In both configurations URLs that match would pass in the path variable (and convert it) into checkUserId method.
For example, if the URL were /user/123/resource, then the id passed in would be 123.

11.3.3 Method Security Expressions

Method security is a bit more complicated than a simple allow or deny rule.
Spring Security 3.0 introduced some new annotations in order to allow comprehensive support for the use of expressions.

@Pre and @Post Annotations

There are four annotations which support expression attributes to allow pre and post-invocation authorization checks and also to support filtering of submitted collection arguments or return values.
They are @PreAuthorize, @PreFilter, @PostAuthorize and @PostFilter.
Their use is enabled through the global-method-security namespace element:

<global-method-securitypre-post-annotations="enabled"/>

Access Control using @PreAuthorize and @PostAuthorize

The most obviously useful annotation is @PreAuthorize which decides whether a method can actually be invoked or not.
For example (from the"Contacts" sample application)

@PreAuthorize("hasRole('USER')")publicvoid create(Contact contact);

which means that access will only be allowed for users with the role "ROLE_USER".
Obviously the same thing could easily be achieved using a traditional configuration and a simple configuration attribute for the required role.
But what about:

Here we’re actually using a method argument as part of the expression to decide whether the current user has the "admin"permission for the given contact.
The built-in hasPermission() expression is linked into the Spring Security ACL module through the application context, as we’llsee below.
You can access any of the method arguments by name as expression variables.

There are a number of ways in which Spring Security can resolve the method arguments.
Spring Security uses DefaultSecurityParameterNameDiscoverer to discover the parameter names.
By default, the following options are tried for a method as a whole.

If Spring Security’s @P annotation is present on a single argument to the method, the value will be used.
This is useful for interfaces compiled with a JDK prior to JDK 8 which do not contain any information about the parameter names.
For example:

Behind the scenes this use implemented using AnnotationParameterNameDiscoverer which can be customized to support the value attribute of any specified annotation.

If Spring Data’s @Param annotation is present on at least one parameter for the method, the value will be used.
This is useful for interfaces compiled with a JDK prior to JDK 8 which do not contain any information about the parameter names.
For example:

Behind the scenes this use implemented using AnnotationParameterNameDiscoverer which can be customized to support the value attribute of any specified annotation.

If JDK 8 was used to compile the source with the -parameters argument and Spring 4+ is being used, then the standard JDK reflection API is used to discover the parameter names.
This works on both classes and interfaces.

Last, if the code was compiled with the debug symbols, the parameter names will be discovered using the debug symbols.
This will not work for interfaces since they do not have debug information about the parameter names.
For interfaces, annotations or the JDK 8 approach must be used.

Any Spring-EL functionality is available within the expression, so you can also access properties on the arguments.
For example, if you wanted a particular method to only allow access to a user whose username matched that of the contact, you could write

Here we are accessing another built-in expression, authentication, which is the Authentication stored in the security context.
You can also access its "principal" property directly, using the expression principal.
The value will often be a UserDetails instance, so you might use an expression like principal.username or principal.enabled.

Less commonly, you may wish to perform an access-control check after the method has been invoked.
This can be achieved using the @PostAuthorize annotation.
To access the return value from a method, use the built-in name returnObject in the expression.

Filtering using @PreFilter and @PostFilter

As you may already be aware, Spring Security supports filtering of collections and arrays and this can now be achieved using expressions.
This is most commonly performed on the return value of a method.
For example:

When using the @PostFilter annotation, Spring Security iterates through the returned collection and removes any elements for which the supplied expression is false.
The name filterObject refers to the current object in the collection.
You can also filter before the method call, using @PreFilter, though this is a less common requirement.
The syntax is just the same, but if there is more than one argument which is a collection type then you have to select one by name using the filterTarget property of this annotation.

Note that filtering is obviously not a substitute for tuning your data retrieval queries.
If you are filtering large collections and removing many of the entries then this is likely to be inefficient.

Built-In Expressions

There are some built-in expressions which are specific to method security, which we have already seen in use above.
The filterTarget and returnValue values are simple enough, but the use of the hasPermission() expression warrants a closer look.

The PermissionEvaluator interface

hasPermission() expressions are delegated to an instance of PermissionEvaluator.
It is intended to bridge between the expression system and Spring Security’s ACL system, allowing you to specify authorization constraints on domain objects, based on abstract permissions.
It has no explicit dependencies on the ACL module, so you could swap that out for an alternative implementation if required.
The interface has two methods:

which map directly to the available versions of the expression, with the exception that the first argument (the Authentication object) is not supplied.
The first is used in situations where the domain object, to which access is being controlled, is already loaded.
Then expression will return true if the current user has the given permission for that object.
The second version is used in cases where the object is not loaded, but its identifier is known.
An abstract "type" specifier for the domain object is also required, allowing the correct ACL permissions to be loaded.
This has traditionally been the Java class of the object, but does not have to be as long as it is consistent with how the permissions are loaded.

To use hasPermission() expressions, you have to explicitly configure a PermissionEvaluator in your application context.
This would look something like this:

Where myPermissionEvaluator is the bean which implements PermissionEvaluator.
Usually this will be the implementation from the ACL module which is called AclPermissionEvaluator.
See the "Contacts" sample application configuration for more details.

Method Security Meta Annotations

You can make use of meta annotations for method security to make your code more readable.
This is especially convenient if you find that you are repeating the same complex expression throughout your code base.
For example, consider the following:

@PreAuthorize("#contact.name == authentication.name")

Instead of repeating this everywhere, we can create a meta annotation that can be used instead.

Meta annotations can be used for any of the Spring Security method security annotations.
In order to remain compliant with the specification JSR-250 annotations do not support meta annotations.

12. Additional Topics

In this part we cover features which require knowledge of previous chapters as well as some of the more advanced and less-commonly used features of the framework.

12.1 Domain Object Security (ACLs)

12.1.1 Overview

Complex applications often will find the need to define access permissions not simply at a web request or method invocation level.
Instead, security decisions need to comprise both who (Authentication), where (MethodInvocation) and what (SomeDomainObject).
In other words, authorization decisions also need to consider the actual domain object instance subject of a method invocation.

Imagine you’re designing an application for a pet clinic.
There will be two main groups of users of your Spring-based application: staff of the pet clinic, as well as the pet clinic’s customers.
The staff will have access to all of the data, whilst your customers will only be able to see their own customer records.
To make it a little more interesting, your customers can allow other users to see their customer records, such as their "puppy preschool" mentor or president of their local "Pony Club".
Using Spring Security as the foundation, you have several approaches that can be used:

Write your business methods to enforce the security.
You could consult a collection within the Customer domain object instance to determine which users have access.
By using the SecurityContextHolder.getContext().getAuthentication(), you’ll be able to access the Authentication object.

Write an AccessDecisionVoter to enforce the security from the GrantedAuthority[] s stored in the Authentication object.
This would mean your AuthenticationManager would need to populate the Authentication with custom GrantedAuthority[]s representing each of the Customer domain object instances the principal has access to.

Write an AccessDecisionVoter to enforce the security and open the target Customer domain object directly.
This would mean your voter needs access to a DAO that allows it to retrieve the Customer object.
It would then access the Customer object’s collection of approved users and make the appropriate decision.

Each one of these approaches is perfectly legitimate.
However, the first couples your authorization checking to your business code.
The main problems with this include the enhanced difficulty of unit testing and the fact it would be more difficult to reuse the Customer authorization logic elsewhere.
Obtaining the GrantedAuthority[] s from the Authentication object is also fine, but will not scale to large numbers of Customer s.
If a user might be able to access 5,000 Customer s (unlikely in this case, but imagine if it were a popular vet for a large Pony Club!) the amount of memory consumed and time required to construct the Authentication object would be undesirable.
The final method, opening the Customer directly from external code, is probably the best of the three.
It achieves separation of concerns, and doesn’t misuse memory or CPU cycles, but it is still inefficient in that both the AccessDecisionVoter and the eventual business method itself will perform a call to the DAO responsible for retrieving the Customer object.
Two accesses per method invocation is clearly undesirable.
In addition, with every approach listed you’ll need to write your own access control list (ACL) persistence and business logic from scratch.

Fortunately, there is another alternative, which we’ll talk about below.

12.1.2 Key Concepts

Spring Security’s ACL services are shipped in the spring-security-acl-xxx.jar.
You will need to add this JAR to your classpath to use Spring Security’s domain object instance security capabilities.

Spring Security’s domain object instance security capabilities centre on the concept of an access control list (ACL).
Every domain object instance in your system has its own ACL, and the ACL records details of who can and can’t work with that domain object.
With this in mind, Spring Security delivers three main ACL-related capabilities to your application:

A way of efficiently retrieving ACL entries for all of your domain objects (and modifying those ACLs)

A way of ensuring a given principal is permitted to work with your objects, before methods are called

A way of ensuring a given principal is permitted to work with your objects (or something they return), after methods are called

As indicated by the first bullet point, one of the main capabilities of the Spring Security ACL module is providing a high-performance way of retrieving ACLs.
This ACL repository capability is extremely important, because every domain object instance in your system might have several access control entries, and each ACL might inherit from other ACLs in a tree-like structure (this is supported out-of-the-box by Spring Security, and is very commonly used).
Spring Security’s ACL capability has been carefully designed to provide high performance retrieval of ACLs, together with pluggable caching, deadlock-minimizing database updates, independence from ORM frameworks (we use JDBC directly), proper encapsulation, and transparent database updating.

Given databases are central to the operation of the ACL module, let’s explore the four main tables used by default in the implementation.
The tables are presented below in order of size in a typical Spring Security ACL deployment, with the table with the most rows listed last:

ACL_SID allows us to uniquely identify any principal or authority in the system ("SID" stands for "security identity").
The only columns are the ID, a textual representation of the SID, and a flag to indicate whether the textual representation refers to a principal name or a GrantedAuthority.
Thus, there is a single row for each unique principal or GrantedAuthority.
When used in the context of receiving a permission, a SID is generally called a "recipient".

ACL_CLASS allows us to uniquely identify any domain object class in the system.
The only columns are the ID and the Java class name.
Thus, there is a single row for each unique Class we wish to store ACL permissions for.

ACL_OBJECT_IDENTITY stores information for each unique domain object instance in the system.
Columns include the ID, a foreign key to the ACL_CLASS table, a unique identifier so we know which ACL_CLASS instance we’re providing information for, the parent, a foreign key to the ACL_SID table to represent the owner of the domain object instance, and whether we allow ACL entries to inherit from any parent ACL.
We have a single row for every domain object instance we’re storing ACL permissions for.

Finally, ACL_ENTRY stores the individual permissions assigned to each recipient.
Columns include a foreign key to the ACL_OBJECT_IDENTITY, the recipient (ie a foreign key to ACL_SID), whether we’ll be auditing or not, and the integer bit mask that represents the actual permission being granted or denied.
We have a single row for every recipient that receives a permission to work with a domain object.

As mentioned in the last paragraph, the ACL system uses integer bit masking.
Don’t worry, you need not be aware of the finer points of bit shifting to use the ACL system, but suffice to say that we have 32 bits we can switch on or off.
Each of these bits represents a permission, and by default the permissions are read (bit 0), write (bit 1), create (bit 2), delete (bit 3) and administer (bit 4).
It’s easy to implement your own Permission instance if you wish to use other permissions, and the remainder of the ACL framework will operate without knowledge of your extensions.

It is important to understand that the number of domain objects in your system has absolutely no bearing on the fact we’ve chosen to use integer bit masking.
Whilst you have 32 bits available for permissions, you could have billions of domain object instances (which will mean billions of rows in ACL_OBJECT_IDENTITY and quite probably ACL_ENTRY).
We make this point because we’ve found sometimes people mistakenly believe they need a bit for each potential domain object, which is not the case.

Now that we’ve provided a basic overview of what the ACL system does, and what it looks like at a table structure, let’s explore the key interfaces.
The key interfaces are:

Acl: Every domain object has one and only one Acl object, which internally holds the AccessControlEntry s as well as knows the owner of the Acl.
An Acl does not refer directly to the domain object, but instead to an ObjectIdentity.
The Acl is stored in the ACL_OBJECT_IDENTITY table.

AccessControlEntry: An Acl holds multiple AccessControlEntry s, which are often abbreviated as ACEs in the framework.
Each ACE refers to a specific tuple of Permission, Sid and Acl.
An ACE can also be granting or non-granting and contain audit settings.
The ACE is stored in the ACL_ENTRY table.

Sid: The ACL module needs to refer to principals and GrantedAuthority[] s.
A level of indirection is provided by the Sid interface, which is an abbreviation of "security identity".
Common classes include PrincipalSid (to represent the principal inside an Authentication object) and GrantedAuthoritySid.
The security identity information is stored in the ACL_SID table.

ObjectIdentity: Each domain object is represented internally within the ACL module by an ObjectIdentity.
The default implementation is called ObjectIdentityImpl.

AclService: Retrieves the Acl applicable for a given ObjectIdentity.
In the included implementation (JdbcAclService), retrieval operations are delegated to a LookupStrategy.
The LookupStrategy provides a highly optimized strategy for retrieving ACL information, using batched retrievals (BasicLookupStrategy) and supporting custom implementations that leverage materialized views, hierarchical queries and similar performance-centric, non-ANSI SQL capabilities.

MutableAclService: Allows a modified Acl to be presented for persistence.
It is not essential to use this interface if you do not wish.

Please note that our out-of-the-box AclService and related database classes all use ANSI SQL.
This should therefore work with all major databases.
At the time of writing, the system had been successfully tested using Hypersonic SQL, PostgreSQL, Microsoft SQL Server and Oracle.

Two samples ship with Spring Security that demonstrate the ACL module.
The first is the Contacts Sample, and the other is the Document Management System (DMS) Sample.
We suggest taking a look over these for examples.

12.1.3 Getting Started

To get starting using Spring Security’s ACL capability, you will need to store your ACL information somewhere.
This necessitates the instantiation of a DataSource using Spring.
The DataSource is then injected into a JdbcMutableAclService and BasicLookupStrategy instance.
The latter provides high-performance ACL retrieval capabilities, and the former provides mutator capabilities.
Refer to one of the samples that ship with Spring Security for an example configuration.
You’ll also need to populate the database with the four ACL-specific tables listed in the last section (refer to the ACL samples for the appropriate SQL statements).

Once you’ve created the required schema and instantiated JdbcMutableAclService, you’ll next need to ensure your domain model supports interoperability with the Spring Security ACL package.
Hopefully ObjectIdentityImpl will prove sufficient, as it provides a large number of ways in which it can be used.
Most people will have domain objects that contain a public Serializable getId() method.
If the return type is long, or compatible with long (eg an int), you will find you need not give further consideration to ObjectIdentity issues.
Many parts of the ACL module rely on long identifiers.
If you’re not using long (or an int, byte etc), there is a very good chance you’ll need to reimplement a number of classes.
We do not intend to support non-long identifiers in Spring Security’s ACL module, as longs are already compatible with all database sequences, the most common identifier data type, and are of sufficient length to accommodate all common usage scenarios.

The following fragment of code shows how to create an Acl, or modify an existing Acl:

In the example above, we’re retrieving the ACL associated with the "Foo" domain object with identifier number 44.
We’re then adding an ACE so that a principal named "Samantha" can "administer" the object.
The code fragment is relatively self-explanatory, except the insertAce method.
The first argument to the insertAce method is determining at what position in the Acl the new entry will be inserted.
In the example above, we’re just putting the new ACE at the end of the existing ACEs.
The final argument is a Boolean indicating whether the ACE is granting or denying.
Most of the time it will be granting (true), but if it is denying (false), the permissions are effectively being blocked.

Spring Security does not provide any special integration to automatically create, update or delete ACLs as part of your DAO or repository operations.
Instead, you will need to write code like shown above for your individual domain objects.
It’s worth considering using AOP on your services layer to automatically integrate the ACL information with your services layer operations.
We’ve found this quite an effective approach in the past.

Once you’ve used the above techniques to store some ACL information in the database, the next step is to actually use the ACL information as part of authorization decision logic.
You have a number of choices here.
You could write your own AccessDecisionVoter or AfterInvocationProvider that respectively fires before or after a method invocation.
Such classes would use AclService to retrieve the relevant ACL and then call Acl.isGranted(Permission[] permission, Sid[] sids, boolean administrativeMode) to decide whether permission is granted or denied.
Alternately, you could use our AclEntryVoter, AclEntryAfterInvocationProvider or AclEntryAfterInvocationCollectionFilteringProvider classes.
All of these classes provide a declarative-based approach to evaluating ACL information at runtime, freeing you from needing to write any code.
Please refer to the sample applications to learn how to use these classes.

12.2 Pre-Authentication Scenarios

There are situations where you want to use Spring Security for authorization, but the user has already been reliably authenticated by some external system prior to accessing the application.
We refer to these situations as "pre-authenticated" scenarios.
Examples include X.509, Siteminder and authentication by the Java EE container in which the application is running.
When using pre-authentication, Spring Security has to

Identify the user making the request.

Obtain the authorities for the user.

The details will depend on the external authentication mechanism.
A user might be identified by their certificate information in the case of X.509, or by an HTTP request header in the case of Siteminder.
If relying on container authentication, the user will be identified by calling the getUserPrincipal() method on the incoming HTTP request.
In some cases, the external mechanism may supply role/authority information for the user but in others the authorities must be obtained from a separate source, such as a UserDetailsService.

12.2.1 Pre-Authentication Framework Classes

Because most pre-authentication mechanisms follow the same pattern, Spring Security has a set of classes which provide an internal framework for implementing pre-authenticated authentication providers.
This removes duplication and allows new implementations to be added in a structured fashion, without having to write everything from scratch.
You don’t need to know about these classes if you want to use something like X.509 authentication, as it already has a namespace configuration option which is simpler to use and get started with.
If you need to use explicit bean configuration or are planning on writing your own implementation then an understanding of how the provided implementations work will be useful.
You will find classes under the org.springframework.security.web.authentication.preauth.
We just provide an outline here so you should consult the Javadoc and source where appropriate.

AbstractPreAuthenticatedProcessingFilter

This class will check the current contents of the security context and, if empty, it will attempt to extract user information from the HTTP request and submit it to the AuthenticationManager.
Subclasses override the following methods to obtain this information:

After calling these, the filter will create a PreAuthenticatedAuthenticationToken containing the returned data and submit it for authentication.
By "authentication" here, we really just mean further processing to perhaps load the user’s authorities, but the standard Spring Security authentication architecture is followed.

Like other Spring Security authentication filters, the pre-authentication filter has an authenticationDetailsSource property which by default will create a WebAuthenticationDetails object to store additional information such as the session-identifier and originating IP address in the details property of the Authentication object.
In cases where user role information can be obtained from the pre-authentication mechanism, the data is also stored in this property, with the details implementing the GrantedAuthoritiesContainer interface.
This enables the authentication provider to read the authorities which were externally allocated to the user.
We’ll look at a concrete example next.

J2eeBasedPreAuthenticatedWebAuthenticationDetailsSource

If the filter is configured with an authenticationDetailsSource which is an instance of this class, the authority information is obtained by calling the isUserInRole(String role) method for each of a pre-determined set of "mappable roles".
The class gets these from a configured MappableAttributesRetriever.
Possible implementations include hard-coding a list in the application context and reading the role information from the <security-role> information in a web.xml file.
The pre-authentication sample application uses the latter approach.

There is an additional stage where the roles (or attributes) are mapped to Spring Security GrantedAuthority objects using a configured Attributes2GrantedAuthoritiesMapper.
The default will just add the usual ROLE_ prefix to the names, but it gives you full control over the behaviour.

PreAuthenticatedAuthenticationProvider

The pre-authenticated provider has little more to do than load the UserDetails object for the user.
It does this by delegating to an AuthenticationUserDetailsService.
The latter is similar to the standard UserDetailsService but takes an Authentication object rather than just user name:

This interface may have also other uses but with pre-authentication it allows access to the authorities which were packaged in the Authentication object, as we saw in the previous section.
The PreAuthenticatedGrantedAuthoritiesUserDetailsService class does this.
Alternatively, it may delegate to a standard UserDetailsService via the UserDetailsByNameServiceWrapper implementation.

Http403ForbiddenEntryPoint

The AuthenticationEntryPoint was discussed in the technical overview chapter.
Normally it is responsible for kick-starting the authentication process for an unauthenticated user (when they try to access a protected resource), but in the pre-authenticated case this doesn’t apply.
You would only configure the ExceptionTranslationFilter with an instance of this class if you aren’t using pre-authentication in combination with other authentication mechanisms.
It will be called if the user is rejected by the AbstractPreAuthenticatedProcessingFilter resulting in a null authentication.
It always returns a 403-forbidden response code if called.

12.2.2 Concrete Implementations

X.509 authentication is covered in its own chapter.
Here we’ll look at some classes which provide support for other pre-authenticated scenarios.

Request-Header Authentication (Siteminder)

An external authentication system may supply information to the application by setting specific headers on the HTTP request.
A well-known example of this is Siteminder, which passes the username in a header called SM_USER.
This mechanism is supported by the class RequestHeaderAuthenticationFilter which simply extracts the username from the header.
It defaults to using the name SM_USER as the header name.
See the Javadoc for more details.

Tip

Note that when using a system like this, the framework performs no authentication checks at all and it is extremely important that the external system is configured properly and protects all access to the application.
If an attacker is able to forge the headers in their original request without this being detected then they could potentially choose any username they wished.

We’ve assumed here that the security namespace is being used for configuration.
It’s also assumed that you have added a UserDetailsService (called "userDetailsService") to your configuration to load the user’s roles.

There is a sample application in the codebase which uses this approach, so get hold of the code from github and have a look at the application context file if you are interested.
The code is in the samples/xml/preauth directory.

12.3 LDAP Authentication

12.3.1 Overview

LDAP is often used by organizations as a central repository for user information and as an authentication service.
It can also be used to store the role information for application users.

There are many different scenarios for how an LDAP server may be configured so Spring Security’s LDAP provider is fully configurable.
It uses separate strategy interfaces for authentication and role retrieval and provides default implementations which can be configured to handle a wide range of situations.

You should be familiar with LDAP before trying to use it with Spring Security.
The following link provides a good introduction to the concepts involved and a guide to setting up a directory using the free LDAP server OpenLDAP: http://www.zytrax.com/books/ldap/.
Some familiarity with the JNDI APIs used to access LDAP from Java may also be useful.
We don’t use any third-party LDAP libraries (Mozilla, JLDAP etc.) in the LDAP provider, but extensive use is made of Spring LDAP, so some familiarity with that project may be useful if you plan on adding your own customizations.

When using LDAP authentication, it is important to ensure that you configure LDAP connection pooling properly.
If you are unfamiliar with how to do this, you can refer to the Java LDAP documentation.

12.3.2 Using LDAP with Spring Security

LDAP authentication in Spring Security can be roughly divided into the following stages.

Obtaining the unique LDAP "Distinguished Name", or DN, from the login name.
This will often mean performing a search in the directory, unless the exact mapping of usernames to DNs is known in advance.
So a user might enter the name "joe" when logging in, but the actual name used to authenticate to LDAP will be the full DN, such as uid=joe,ou=users,dc=spring,dc=io.

Authenticating the user, either by "binding" as that user or by performing a remote "compare" operation of the user’s password against the password attribute in the directory entry for the DN.

Loading the list of authorities for the user.

The exception is when the LDAP directory is just being used to retrieve user information and authenticate against it locally.
This may not be possible as directories are often set up with limited read access for attributes such as user passwords.

We will look at some configuration scenarios below.
For full information on available configuration options, please consult the security namespace schema (information from which should be available in your XML editor).

12.3.3 Configuring an LDAP Server

The first thing you need to do is configure the server against which authentication should take place.
This is done using the <ldap-server> element from the security namespace.
This can be configured to point at an external LDAP server, using the url attribute:

Using an Embedded Test Server

The <ldap-server> element can also be used to create an embedded server, which can be very useful for testing and demonstrations.
In this case you use it without the url attribute:

<ldap-serverroot="dc=springframework,dc=org"/>

Here we’ve specified that the root DIT of the directory should be "dc=springframework,dc=org", which is the default.
Used this way, the namespace parser will create an embedded Apache Directory server and scan the classpath for any LDIF files, which it will attempt to load into the server.
You can customize this behaviour using the ldif attribute, which defines an LDIF resource to be loaded:

<ldap-serverldif="classpath:users.ldif" />

This makes it a lot easier to get up and running with LDAP, since it can be inconvenient to work all the time with an external server.
It also insulates the user from the complex bean configuration needed to wire up an Apache Directory server.
Using plain Spring Beans the configuration would be much more cluttered.
You must have the necessary Apache Directory dependency jars available for your application to use.
These can be obtained from the LDAP sample application.

Using Bind Authentication

This is the most common LDAP authentication scenario.

<ldap-authentication-provideruser-dn-pattern="uid={0},ou=people"/>

This simple example would obtain the DN for the user by substituting the user login name in the supplied pattern and attempting to bind as that user with the login password.
This is OK if all your users are stored under a single node in the directory.
If instead you wished to configure an LDAP search filter to locate the user, you could use the following:

If used with the server definition above, this would perform a search under the DN ou=people,dc=springframework,dc=org using the value of the user-search-filter attribute as a filter.
Again the user login name is substituted for the parameter in the filter name, so it will search for an entry with the uid attribute equal to the user name.
If user-search-base isn’t supplied, the search will be performed from the root.

Loading Authorities

How authorities are loaded from groups in the LDAP directory is controlled by the following attributes.

group-search-base.
Defines the part of the directory tree under which group searches should be performed.

group-role-attribute.
The attribute which contains the name of the authority defined by the group entry.
Defaults to cn

group-search-filter.
The filter which is used to search for group membership.
The default is uniqueMember={0}, corresponding to the groupOfUniqueNames LDAP class [19].
In this case, the substituted parameter is the full distinguished name of the user.
The parameter {1} can be used if you want to filter on the login name.

and authenticated successfully as user "ben", the subsequent loading of authorities would perform a search under the directory entry ou=groups,dc=springframework,dc=org, looking for entries which contain the attribute uniqueMember with value uid=ben,ou=people,dc=springframework,dc=org.
By default the authority names will have the prefix ROLE_ prepended.
You can change this using the role-prefix attribute.
If you don’t want any prefix, use role-prefix="none".
For more information on loading authorities, see the Javadoc for the DefaultLdapAuthoritiesPopulator class.

12.3.4 Implementation Classes

The namespace configuration options we’ve used above are simple to use and much more concise than using Spring beans explicitly.
There are situations when you may need to know how to configure Spring Security LDAP directly in your application context.
You may wish to customize the behaviour of some of the classes, for example.
If you’re happy using namespace configuration then you can skip this section and the next one.

The main LDAP provider class, LdapAuthenticationProvider, doesn’t actually do much itself but delegates the work to two other beans, an LdapAuthenticator and an LdapAuthoritiesPopulator which are responsible for authenticating the user and retrieving the user’s set of GrantedAuthority s respectively.

LdapAuthenticator Implementations

The authenticator is also responsible for retrieving any required user attributes.
This is because the permissions on the attributes may depend on the type of authentication being used.
For example, if binding as the user, it may be necessary to read them with the user’s own permissions.

There are currently two authentication strategies supplied with Spring Security:

Authentication directly to the LDAP server ("bind" authentication).

Password comparison, where the password supplied by the user is compared with the one stored in the repository.
This can either be done by retrieving the value of the password attribute and checking it locally or by performing an LDAP "compare" operation, where the supplied password is passed to the server for comparison and the real password value is never retrieved.

Common Functionality

Before it is possible to authenticate a user (by either strategy), the distinguished name (DN) has to be obtained from the login name supplied to the application.
This can be done either by simple pattern-matching (by setting the setUserDnPatterns array property) or by setting the userSearch property.
For the DN pattern-matching approach, a standard Java pattern format is used, and the login name will be substituted for the parameter {0}.
The pattern should be relative to the DN that the configured SpringSecurityContextSource will bind to (see the section on connecting to the LDAP server for more information on this).
For example, if you are using an LDAP server with the URL ldap://monkeymachine.co.uk/dc=springframework,dc=org, and have a pattern uid={0},ou=greatapes, then a login name of "gorilla" will map to a DN uid=gorilla,ou=greatapes,dc=springframework,dc=org.
Each configured DN pattern will be tried in turn until a match is found.
For information on using a search, see the section on search objects below.
A combination of the two approaches can also be used - the patterns will be checked first and if no matching DN is found, the search will be used.

BindAuthenticator

The class BindAuthenticator in the package org.springframework.security.ldap.authentication implements the bind authentication strategy.
It simply attempts to bind as the user.

PasswordComparisonAuthenticator

Connecting to the LDAP Server

The beans discussed above have to be able to connect to the server.
They both have to be supplied with a SpringSecurityContextSource which is an extension of Spring LDAP’s ContextSource.
Unless you have special requirements, you will usually configure a DefaultSpringSecurityContextSource bean, which can be configured with the URL of your LDAP server and optionally with the username and password of a "manager" user which will be used by default when binding to the server (instead of binding anonymously).
For more information read the Javadoc for this class and for Spring LDAP’s AbstractContextSource.

LDAP Search Objects

Often a more complicated strategy than simple DN-matching is required to locate a user entry in the directory.
This can be encapsulated in an LdapUserSearch instance which can be supplied to the authenticator implementations, for example, to allow them to locate a user.
The supplied implementation is FilterBasedLdapUserSearch.

FilterBasedLdapUserSearch

This bean uses an LDAP filter to match the user object in the directory.
The process is explained in the Javadoc for the corresponding search method on the JDK DirContext class.
As explained there, the search filter can be supplied with parameters.
For this class, the only valid parameter is {0} which will be replaced with the user’s login name.

LdapAuthoritiesPopulator

After authenticating the user successfully, the LdapAuthenticationProvider will attempt to load a set of authorities for the user by calling the configured LdapAuthoritiesPopulator bean.
The DefaultLdapAuthoritiesPopulator is an implementation which will load the authorities by searching the directory for groups of which the user is a member (typically these will be groupOfNames or groupOfUniqueNames entries in the directory).
Consult the Javadoc for this class for more details on how it works.

If you want to use LDAP only for authentication, but load the authorities from a difference source (such as a database) then you can provide your own implementation of this interface and inject that instead.

Spring Bean Configuration

A typical configuration, using some of the beans we’ve discussed here, might look like this:

This would set up the provider to access an LDAP server with URL ldap://monkeymachine:389/dc=springframework,dc=org.
Authentication will be performed by attempting to bind with the DN uid=<user-login-name>,ou=people,dc=springframework,dc=org.
After successful authentication, roles will be assigned to the user by searching under the DN ou=groups,dc=springframework,dc=org with the default filter (member=<user’s-DN>).
The role name will be taken from the "ou" attribute of each match.

To configure a user search object, which uses the filter (uid=<user-login-name>) for use instead of the DN-pattern (or in addition to it), you would configure the following bean

and use it by setting the BindAuthenticator bean’s userSearch property.
The authenticator would then call the search object to obtain the correct user’s DN before attempting to bind as this user.

LDAP Attributes and Customized UserDetails

The net result of an authentication using LdapAuthenticationProvider is the same as a normal Spring Security authentication using the standard UserDetailsService interface.
A UserDetails object is created and stored in the returned Authentication object.
As with using a UserDetailsService, a common requirement is to be able to customize this implementation and add extra properties.
When using LDAP, these will normally be attributes from the user entry.
The creation of the UserDetails object is controlled by the provider’s UserDetailsContextMapper strategy, which is responsible for mapping user objects to and from LDAP context data:

Only the first method is relevant for authentication.
If you provide an implementation of this interface and inject it into the LdapAuthenticationProvider, you have control over exactly how the UserDetails object is created.
The first parameter is an instance of Spring LDAP’s DirContextOperations which gives you access to the LDAP attributes which were loaded during authentication.
The username parameter is the name used to authenticate and the final parameter is the collection of authorities loaded for the user by the configured LdapAuthoritiesPopulator.

The way the context data is loaded varies slightly depending on the type of authentication you are using.
With the BindAuthenticator, the context returned from the bind operation will be used to read the attributes, otherwise the data will be read using the standard context obtained from the configured ContextSource (when a search is configured to locate the user, this will be the data returned by the search object).

12.3.5 Active Directory Authentication

Active Directory supports its own non-standard authentication options, and the normal usage pattern doesn’t fit too cleanly with the standard LdapAuthenticationProvider.
Typically authentication is performed using the domain username (in the form [email protected]), rather than using an LDAP distinguished name.
To make this easier, Spring Security 3.1 has an authentication provider which is customized for a typical Active Directory setup.

ActiveDirectoryLdapAuthenticationProvider

Configuring ActiveDirectoryLdapAuthenticationProvider is quite straightforward.
You just need to supply the domain name and an LDAP URL supplying the address of the server [20].
An example configuration would then look like this:

Note that there is no need to specify a separate ContextSource in order to define the server location - the bean is completely self-contained.
A user named "Sharon", for example, would then be able to authenticate by entering either the username sharon or the full Active Directory userPrincipalName, namely [email protected].
The user’s directory entry will then be located, and the attributes returned for possible use in customizing the created UserDetails object (a UserDetailsContextMapper can be injected for this purpose, as described above).
All interaction with the directory takes place with the identity of the user themselves.
There is no concept of a "manager" user.

By default, the user authorities are obtained from the memberOf attribute values of the user entry.
The authorities allocated to the user can again be customized using a UserDetailsContextMapper.
You can also inject a GrantedAuthoritiesMapper into the provider instance to control the authorities which end up in the Authentication object.

Active Directory Error Codes

By default, a failed result will cause a standard Spring Security BadCredentialsException.
If you set the property convertSubErrorCodesToExceptions to true, the exception messages will be parsed to attempt to extract the Active Directory-specific error code and raise a more specific exception.
Check the class Javadoc for more information.

12.4 OAuth 2.0 Login — Advanced Configuration

HttpSecurity.oauth2Login() provides a number of configuration options for customizing OAuth 2.0 Login.
The main configuration options are grouped into their protocol endpoint counterparts.

The UserInfo Endpoint is an OAuth 2.0 Protected Resource that returns claims about the authenticated end-user.
To obtain the requested claims about the end-user, the client makes a request to the UserInfo Endpoint by using an access token obtained through OpenID Connect Authentication.
These claims are normally represented by a JSON object that contains a collection of name-value pairs for the claims.

The following code shows the complete configuration options available for the oauth2Login() DSL:

12.4.1 OAuth 2.0 Login Page

By default, the OAuth 2.0 Login Page is auto-generated by the DefaultLoginPageGeneratingFilter.
The default login page shows each configured OAuth Client with its ClientRegistration.clientName as a link, which is capable of initiating the Authorization Request (or OAuth 2.0 Login).

The link’s destination for each OAuth Client defaults to the following:

You need to provide a @Controller with a @RequestMapping("/login/oauth2") that is capable of rendering the custom login page.

Tip

As noted earlier, configuring oauth2Login().authorizationEndpoint().baseUri() is optional.
However, if you choose to customize it, ensure the link to each OAuth Client matches the authorizationEndpoint().baseUri().

The following line shows an example:

<a href="/login/oauth2/authorization/google">Google</a>

12.4.2 Redirection Endpoint

The Redirection Endpoint is used by the Authorization Server for returning the Authorization Response (which contains the authorization credentials) to the client via the Resource Owner user-agent.

Mapping User Authorities

After the user successfully authenticates with the OAuth 2.0 Provider, the OAuth2User.getAuthorities() (or OidcUser.getAuthorities()) may be mapped to a new set of GrantedAuthority instances, which will be supplied to OAuth2AuthenticationToken when completing the authentication.

Tip

OAuth2AuthenticationToken.getAuthorities() is used for authorizing requests, such as in hasRole('USER') or hasRole('ADMIN').

There are a couple of options to choose from when mapping user authorities:

Delegation-based strategy with OAuth2UserService

This strategy is advanced compared to using a GrantedAuthoritiesMapper, however, it’s also more flexible as it gives you access to the OAuth2UserRequest and OAuth2User (when using an OAuth 2.0 UserService) or OidcUserRequest and OidcUser (when using an OpenID Connect 1.0 UserService).

The OAuth2UserRequest (and OidcUserRequest) provides you access to the associated OAuth2AccessToken, which is very useful in the cases where the delegator needs to fetch authority information from a protected resource before it can map the custom authorities for the user.

The following example shows how to implement and configure a delegation-based strategy using an OpenID Connect 1.0 UserService:

id, name, login, and email are attributes returned in GitHub’s UserInfo Response.
For detailed information returned from the UserInfo Endpoint, see the API documentation
for "Get the authenticated user".

OAuth 2.0 UserService

DefaultOAuth2UserService is an implementation of an OAuth2UserService that supports standard OAuth 2.0 Provider’s.

Note

OAuth2UserService obtains the user attributes of the end-user (the resource owner) from the UserInfo Endpoint (by using the access token granted to the client during the authorization flow) and returns an AuthenticatedPrincipal in the form of an OAuth2User.

DefaultOAuth2UserService uses a RestOperations when requesting the user attributes at the UserInfo Endpoint.

If you need to customize the pre-processing of the UserInfo Request, you can provide DefaultOAuth2UserService.setRequestEntityConverter() with a custom Converter<OAuth2UserRequest, RequestEntity<?>>.
The default implementation OAuth2UserRequestEntityConverter builds a RequestEntity representation of a UserInfo Request that sets the OAuth2AccessToken in the Authorization header by default.

On the other end, if you need to customize the post-handling of the UserInfo Response, you will need to provide DefaultOAuth2UserService.setRestOperations() with a custom configured RestOperations.
The default RestOperations is configured as follows:

OAuth2ErrorResponseErrorHandler is a ResponseErrorHandler that can handle an OAuth 2.0 Error (400 Bad Request).
It uses an OAuth2ErrorHttpMessageConverter for converting the OAuth 2.0 Error parameters to an OAuth2Error.

Whether you customize DefaultOAuth2UserService or provide your own implementation of OAuth2UserService, you’ll need to configure it as shown in the following example:

OpenID Connect 1.0 UserService

OidcUserService is an implementation of an OAuth2UserService that supports OpenID Connect 1.0 Provider’s.

The OidcUserService leverages the DefaultOAuth2UserService when requesting the user attributes at the UserInfo Endpoint.

If you need to customize the pre-processing of the UserInfo Request and/or the post-handling of the UserInfo Response, you will need to provide OidcUserService.setOauth2UserService() with a custom configured DefaultOAuth2UserService.

Whether you customize OidcUserService or provide your own implementation of OAuth2UserService for OpenID Connect 1.0 Provider’s, you’ll need to configure it as shown in the following example:

13.2 Implicit OAuth2AuthorizedClient

If we set defaultOAuth2AuthorizedClient to true in our setup and the user authenticated with oauth2Login (i.e. OIDC), then the current authentication is used to automatically provide the access token.
Alternatively, if we set defaultClientRegistrationId to a valid ClientRegistration id, that registration is used to provide the access token.
This is convenient, but in environments where not all endpoints should get the access token, it is dangerous (you might provide the wrong access token to an endpoint).

13.3 Explicit OAuth2AuthorizedClient

The OAuth2AuthorizedClient can be explicitly provided by setting it on the request attributes.
In the example below we resolve the OAuth2AuthorizedClient using Spring WebFlux or Spring MVC argument resolver support.
However, it does not matter how the OAuth2AuthorizedClient is resolved.

13.4 clientRegistrationId

Alternatively, it is possible to specify the clientRegistrationId on the request attributes and the WebClient will attempt to lookup the OAuth2AuthorizedClient.
If it is not found, one will automatically be acquired.

13.5.1 Declaring the Taglib

13.5.2 The authorize Tag

This tag is used to determine whether its contents should be evaluated or not.
In Spring Security 3.0, it can be used in two ways [21].
The first approach uses a web-security expression, specified in the access attribute of the tag.
The expression evaluation will be delegated to the SecurityExpressionHandler<FilterInvocation> defined in the application context (you should have web expressions enabled in your <http> namespace configuration to make sure this service is available).
So, for example, you might have

<sec:authorizeaccess="hasRole('supervisor')">
This content will only be visible to users who have the "supervisor" authority in their list of <tt>GrantedAuthority</tt>s.
</sec:authorize>

When used in conjuction with Spring Security’s PermissionEvaluator, the tag can also be used to check permissions.
For example:

<sec:authorizeaccess="hasPermission(#domain,'read') or hasPermission(#domain,'write')">
This content will only be visible to users who have read or write permission to the Object found as a request attribute named "domain".
</sec:authorize>

A common requirement is to only show a particular link, if the user is actually allowed to click it.
How can we determine in advance whether something will be allowed? This tag can also operate in an alternative mode which allows you to define a particular URL as an attribute.
If the user is allowed to invoke that URL, then the tag body will be evaluated, otherwise it will be skipped.
So you might have something like

<sec:authorizeurl="/admin">
This content will only be visible to users who are authorized to send requests to the "/admin" URL.
</sec:authorize>

To use this tag there must also be an instance of WebInvocationPrivilegeEvaluator in your application context.
If you are using the namespace, one will automatically be registered.
This is an instance of DefaultWebInvocationPrivilegeEvaluator, which creates a dummy web request for the supplied URL and invokes the security interceptor to see whether the request would succeed or fail.
This allows you to delegate to the access-control setup you defined using intercept-url declarations within the <http> namespace configuration and saves having to duplicate the information (such as the required roles) within your JSPs.
This approach can also be combined with a method attribute, supplying the HTTP method, for a more specific match.

The Boolean result of evaluating the tag (whether it grants or denies access) can be stored in a page context scope variable by setting the var attribute to the variable name, avoiding the need for duplicating and re-evaluating the condition at other points in the page.

Disabling Tag Authorization for Testing

Hiding a link in a page for unauthorized users doesn’t prevent them from accessing the URL.
They could just type it into their browser directly, for example.
As part of your testing process, you may want to reveal the hidden areas in order to check that links really are secured at the back end.
If you set the system property spring.security.disableUISecurity to true, the authorize tag will still run but will not hide its contents.
By default it will also surround the content with <span class="securityHiddenUI">…​</span> tags.
This allows you to display "hidden" content with a particular CSS style such as a different background colour.
Try running the "tutorial" sample application with this property enabled, for example.

You can also set the properties spring.security.securedUIPrefix and spring.security.securedUISuffix if you want to change surrounding text from the default span tags (or use empty strings to remove it completely).

13.5.3 The authentication Tag

This tag allows access to the current Authentication object stored in the security context.
It renders a property of the object directly in the JSP.
So, for example, if the principal property of the Authentication is an instance of Spring Security’s UserDetails object, then using <sec:authentication property="principal.username" /> will render the name of the current user.

Of course, it isn’t necessary to use JSP tags for this kind of thing and some people prefer to keep as little logic as possible in the view.
You can access the Authentication object in your MVC controller (by calling SecurityContextHolder.getContext().getAuthentication()) and add the data directly to your model for rendering by the view.

13.5.4 The accesscontrollist Tag

This tag is only valid when used with Spring Security’s ACL module.
It checks a comma-separated list of required permissions for a specified domain object.
If the current user has all of those permissions, then the tag body will be evaluated.
If they don’t, it will be skipped.
An example might be

<sec:accesscontrollisthasPermission="1,2"domainObject="${someObject}">
This will be shown if the user has all of the permissions represented by the values "1" or "2" on the given object.
</sec:accesscontrollist>

The permissions are passed to the PermissionFactory defined in the application context, converting them to ACL Permission instances, so they may be any format which is supported by the factory - they don’t have to be integers, they could be strings like READ or WRITE.
If no PermissionFactory is found, an instance of DefaultPermissionFactory will be used.
The AclService from the application context will be used to load the Acl instance for the supplied object.
The Acl will be invoked with the required permissions to check if all of them are granted.

This tag also supports the var attribute, in the same way as the authorize tag.

13.5.5 The csrfInput Tag

If CSRF protection is enabled, this tag inserts a hidden form field with the correct name and value for the CSRF protection token.
If CSRF protection is not enabled, this tag outputs nothing.

Normally Spring Security automatically inserts a CSRF form field for any <form:form> tags you use, but if for some reason you cannot use <form:form>, csrfInput is a handy replacement.

You should place this tag within an HTML <form></form> block, where you would normally place other input fields.
Do NOT place this tag within a Spring <form:form></form:form> block.
Spring Security handles Spring forms automatically.

13.5.6 The csrfMetaTags Tag

If CSRF protection is enabled, this tag inserts meta tags containing the CSRF protection token form field and header names and CSRF protection token value.
These meta tags are useful for employing CSRF protection within JavaScript in your applications.

You should place csrfMetaTags within an HTML <head></head> block, where you would normally place other meta tags.
Once you use this tag, you can access the form field name, header name, and token value easily using JavaScript.
JQuery is used in this example to make the task easier.

13.6 Java Authentication and Authorization Service (JAAS) Provider

13.6.1 Overview

Spring Security provides a package able to delegate authentication requests to the Java Authentication and Authorization Service (JAAS).
This package is discussed in detail below.

13.6.2 AbstractJaasAuthenticationProvider

The AbstractJaasAuthenticationProvider is the basis for the provided JAAS AuthenticationProvider implementations.
Subclasses must implement a method that creates the LoginContext.
The AbstractJaasAuthenticationProvider has a number of dependencies that can be injected into it that are discussed below.

JAAS CallbackHandler

Most JAAS LoginModule s require a callback of some sort.
These callbacks are usually used to obtain the username and password from the user.

In a Spring Security deployment, Spring Security is responsible for this user interaction (via the authentication mechanism).
Thus, by the time the authentication request is delegated through to JAAS, Spring Security’s authentication mechanism will already have fully-populated an Authentication object containing all the information required by the JAAS LoginModule.

Therefore, the JAAS package for Spring Security provides two default callback handlers, JaasNameCallbackHandler and JaasPasswordCallbackHandler.
Each of these callback handlers implement JaasAuthenticationCallbackHandler.
In most cases these callback handlers can simply be used without understanding the internal mechanics.

For those needing full control over the callback behavior, internally AbstractJaasAuthenticationProvider wraps these JaasAuthenticationCallbackHandler s with an InternalCallbackHandler.
The InternalCallbackHandler is the class that actually implements JAAS normal CallbackHandler interface.
Any time that the JAAS LoginModule is used, it is passed a list of application context configured InternalCallbackHandler s.
If the LoginModule requests a callback against the InternalCallbackHandler s, the callback is in-turn passed to the JaasAuthenticationCallbackHandler s being wrapped.

JAAS AuthorityGranter

JAAS works with principals.
Even "roles" are represented as principals in JAAS.
Spring Security, on the other hand, works with Authentication objects.
Each Authentication object contains a single principal, and multiple GrantedAuthority s.
To facilitate mapping between these different concepts, Spring Security’s JAAS package includes an AuthorityGranter interface.

An AuthorityGranter is responsible for inspecting a JAAS principal and returning a set of String s, representing the authorities assigned to the principal.
For each returned authority string, the AbstractJaasAuthenticationProvider creates a JaasGrantedAuthority (which implements Spring Security’s GrantedAuthority interface) containing the authority string and the JAAS principal that the AuthorityGranter was passed.
The AbstractJaasAuthenticationProvider obtains the JAAS principals by firstly successfully authenticating the user’s credentials using the JAAS LoginModule, and then accessing the LoginContext it returns.
A call to LoginContext.getSubject().getPrincipals() is made, with each resulting principal passed to each AuthorityGranter defined against the AbstractJaasAuthenticationProvider.setAuthorityGranters(List) property.

Spring Security does not include any production AuthorityGranter s given that every JAAS principal has an implementation-specific meaning.
However, there is a TestAuthorityGranter in the unit tests that demonstrates a simple AuthorityGranter implementation.

13.6.3 DefaultJaasAuthenticationProvider

The DefaultJaasAuthenticationProvider allows a JAAS Configuration object to be injected into it as a dependency.
It then creates a LoginContext using the injected JAAS Configuration.
This means that DefaultJaasAuthenticationProvider is not bound any particular implementation of Configuration as JaasAuthenticationProvider is.

InMemoryConfiguration

In order to make it easy to inject a Configuration into DefaultJaasAuthenticationProvider, a default in-memory implementation named InMemoryConfiguration is provided.
The implementation constructor accepts a Map where each key represents a login configuration name and the value represents an Array of AppConfigurationEntry s.
InMemoryConfiguration also supports a default Array of AppConfigurationEntry objects that will be used if no mapping is found within the provided Map.
For details, refer to the class level javadoc of InMemoryConfiguration.

DefaultJaasAuthenticationProvider Example Configuration

While the Spring configuration for InMemoryConfiguration can be more verbose than the standarad JAAS configuration files, using it in conjuction with DefaultJaasAuthenticationProvider is more flexible than JaasAuthenticationProvider since it not dependant on the default Configuration implementation.

An example configuration of DefaultJaasAuthenticationProvider using InMemoryConfiguration is provided below.
Note that custom implementations of Configuration can easily be injected into DefaultJaasAuthenticationProvider as well.

<beanid="jaasAuthProvider"class="org.springframework.security.authentication.jaas.DefaultJaasAuthenticationProvider"><propertyname="configuration"><beanclass="org.springframework.security.authentication.jaas.memory.InMemoryConfiguration"><constructor-arg><map><!--
SPRINGSECURITY is the default loginContextName
for AbstractJaasAuthenticationProvider
--><entrykey="SPRINGSECURITY"><array><beanclass="javax.security.auth.login.AppConfigurationEntry"><constructor-argvalue="sample.SampleLoginModule" /><constructor-arg><util:constantstatic-field=
"javax.security.auth.login.AppConfigurationEntry$LoginModuleControlFlag.REQUIRED"/></constructor-arg><constructor-arg><map></map></constructor-arg></bean></array></entry></map></constructor-arg></bean></property><propertyname="authorityGranters"><list><!-- You will need to write your own implementation of AuthorityGranter --><beanclass="org.springframework.security.authentication.jaas.TestAuthorityGranter"/></list></property></bean>

13.6.4 JaasAuthenticationProvider

The JaasAuthenticationProvider assumes the default Configuration is an instance of ConfigFile.
This assumption is made in order to attempt to update the Configuration.
The JaasAuthenticationProvider then uses the default Configuration to create the LoginContext.

Let’s assume we have a JAAS login configuration file, /WEB-INF/login.conf, with the following contents:

JAASTest {
sample.SampleLoginModule required;
};

Like all Spring Security beans, the JaasAuthenticationProvider is configured via the application context.
The following definitions would correspond to the above JAAS login configuration file:

13.6.5 Running as a Subject

If configured, the JaasApiIntegrationFilter will attempt to run as the Subject on the JaasAuthenticationToken.
This means that the Subject can be accessed using:

Subject subject = Subject.getSubject(AccessController.getContext());

This integration can easily be configured using the jaas-api-provision attribute.
This feature is useful when integrating with legacy or external API’s that rely on the JAAS Subject being populated.

13.7 CAS Authentication

13.7.1 Overview

JA-SIG produces an enterprise-wide single sign on system known as CAS.
Unlike other initiatives, JA-SIG’s Central Authentication Service is open source, widely used, simple to understand, platform independent, and supports proxy capabilities.
Spring Security fully supports CAS, and provides an easy migration path from single-application deployments of Spring Security through to multiple-application deployments secured by an enterprise-wide CAS server.

You can learn more about CAS at http://www.ja-sig.org/cas.
You will also need to visit this site to download the CAS Server files.

13.7.2 How CAS Works

Whilst the CAS web site contains documents that detail the architecture of CAS, we present the general overview again here within the context of Spring Security.
Spring Security 3.x supports CAS 3.
At the time of writing, the CAS server was at version 3.4.

Somewhere in your enterprise you will need to setup a CAS server.
The CAS server is simply a standard WAR file, so there isn’t anything difficult about setting up your server.
Inside the WAR file you will customise the login and other single sign on pages displayed to users.

When deploying a CAS 3.4 server, you will also need to specify an AuthenticationHandler in the deployerConfigContext.xml included with CAS.
The AuthenticationHandler has a simple method that returns a boolean as to whether a given set of Credentials is valid.
Your AuthenticationHandler implementation will need to link into some type of backend authentication repository, such as an LDAP server or database.
CAS itself includes numerous AuthenticationHandler s out of the box to assist with this.
When you download and deploy the server war file, it is set up to successfully authenticate users who enter a password matching their username, which is useful for testing.

Apart from the CAS server itself, the other key players are of course the secure web applications deployed throughout your enterprise.
These web applications are known as "services".
There are three types of services.
Those that authenticate service tickets, those that can obtain proxy tickets, and those that authenticate proxy tickets.
Authenticating a proxy ticket differs because the list of proxies must be validated and often times a proxy ticket can be reused.

Spring Security and CAS Interaction Sequence

The basic interaction between a web browser, CAS server and a Spring Security-secured service is as follows:

The web user is browsing the service’s public pages.
CAS or Spring Security is not involved.

The user eventually requests a page that is either secure or one of the beans it uses is secure.
Spring Security’s ExceptionTranslationFilter will detect the AccessDeniedException or AuthenticationException.

Because the user’s Authentication object (or lack thereof) caused an AuthenticationException, the ExceptionTranslationFilter will call the configured AuthenticationEntryPoint.
If using CAS, this will be the CasAuthenticationEntryPoint class.

After the user’s browser redirects to CAS, they will be prompted for their username and password.
If the user presents a session cookie which indicates they’ve previously logged on, they will not be prompted to login again (there is an exception to this procedure, which we’ll cover later).
CAS will use the PasswordHandler (or AuthenticationHandler if using CAS 3.0) discussed above to decide whether the username and password is valid.

Back in the service web application, the CasAuthenticationFilter is always listening for requests to /login/cas (this is configurable, but we’ll use the defaults in this introduction).
The processing filter will construct a UsernamePasswordAuthenticationToken representing the service ticket.
The principal will be equal to CasAuthenticationFilter.CAS_STATEFUL_IDENTIFIER, whilst the credentials will be the service ticket opaque value.
This authentication request will then be handed to the configured AuthenticationManager.

The AuthenticationManager implementation will be the ProviderManager, which is in turn configured with the CasAuthenticationProvider.
The CasAuthenticationProvider only responds to UsernamePasswordAuthenticationToken s containing the CAS-specific principal (such as CasAuthenticationFilter.CAS_STATEFUL_IDENTIFIER) and CasAuthenticationToken s (discussed later).

Back on the CAS server, the validation request will be received.
If the presented service ticket matches the service URL the ticket was issued to, CAS will provide an affirmative response in XML indicating the username.
If any proxy was involved in the authentication (discussed below), the list of proxies is also included in the XML response.

The Cas20TicketValidator will parse the XML received from the CAS server.
It will return to the CasAuthenticationProvider a TicketResponse, which includes the username (mandatory), proxy list (if any were involved), and proxy-granting ticket IOU (if the proxy callback was requested).

Next CasAuthenticationProvider will call a configured CasProxyDecider.
The CasProxyDecider indicates whether the proxy list in the TicketResponse is acceptable to the service.
Several implementations are provided with Spring Security: RejectProxyTickets, AcceptAnyCasProxy and NamedCasProxyDecider.
These names are largely self-explanatory, except NamedCasProxyDecider which allows a List of trusted proxies to be provided.

CasAuthenticationProvider will next request a AuthenticationUserDetailsService to load the GrantedAuthority objects that apply to the user contained in the Assertion.

If there were no problems, CasAuthenticationProvider constructs a CasAuthenticationToken including the details contained in the TicketResponse and the GrantedAuthoritys.

Control then returns to CasAuthenticationFilter, which places the created CasAuthenticationToken in the security context.

The user’s browser is redirected to the original page that caused the AuthenticationException (or a custom destination depending on the configuration).

It’s good that you’re still here!
Let’s now look at how this is configured

13.7.3 Configuration of CAS Client

The web application side of CAS is made easy due to Spring Security.
It is assumed you already know the basics of using Spring Security, so these are not covered again below.
We’ll assume a namespace based configuration is being used and add in the CAS beans as required.
Each section builds upon the previous section.
A fullCAS sample application can be found in the Spring Security Samples.

Service Ticket Authentication

This section describes how to setup Spring Security to authenticate Service Tickets.
Often times this is all a web application requires.
You will need to add a ServiceProperties bean to your application context.
This represents your CAS service:

The service must equal a URL that will be monitored by the CasAuthenticationFilter.
The sendRenew defaults to false, but should be set to true if your application is particularly sensitive.
What this parameter does is tell the CAS login service that a single sign on login is unacceptable.
Instead, the user will need to re-enter their username and password in order to gain access to the service.

The following beans should be configured to commence the CAS authentication process (assuming you’re using a namespace configuration):

For CAS to operate, the ExceptionTranslationFilter must have its authenticationEntryPoint property set to the CasAuthenticationEntryPoint bean.
This can easily be done using entry-point-ref as is done in the example above.
The CasAuthenticationEntryPoint must refer to the ServiceProperties bean (discussed above), which provides the URL to the enterprise’s CAS login server.
This is where the user’s browser will be redirected.

The CasAuthenticationFilter has very similar properties to the UsernamePasswordAuthenticationFilter (used for form-based logins).
You can use these properties to customize things like behavior for authentication success and failure.

Next you need to add a CasAuthenticationProvider and its collaborators:

<security:authentication-manageralias="authenticationManager"><security:authentication-providerref="casAuthenticationProvider" /></security:authentication-manager><beanid="casAuthenticationProvider"class="org.springframework.security.cas.authentication.CasAuthenticationProvider"><propertyname="authenticationUserDetailsService"><beanclass="org.springframework.security.core.userdetails.UserDetailsByNameServiceWrapper"><constructor-argref="userService" /></bean></property><propertyname="serviceProperties"ref="serviceProperties" /><propertyname="ticketValidator"><beanclass="org.jasig.cas.client.validation.Cas20ServiceTicketValidator"><constructor-argindex="0"value="https://localhost:9443/cas" /></bean></property><propertyname="key"value="an_id_for_this_auth_provider_only"/></bean><security:user-serviceid="userService"><!-- Password is prefixed with {noop} to indicate to DelegatingPasswordEncoder that
NoOpPasswordEncoder should be used.
This is not safe for production, but makes reading
in samples easier.
Normally passwords should be hashed using BCrypt --><security:username="joe"password="{noop}joe"authorities="ROLE_USER" />
...
</security:user-service>

The CasAuthenticationProvider uses a UserDetailsService instance to load the authorities for a user, once they have been authenticated by CAS.
We’ve shown a simple in-memory setup here.
Note that the CasAuthenticationProvider does not actually use the password for authentication, but it does use the authorities.

The beans are all reasonably self-explanatory if you refer back to the How CAS Works section.

This completes the most basic configuration for CAS.
If you haven’t made any mistakes, your web application should happily work within the framework of CAS single sign on.
No other parts of Spring Security need to be concerned about the fact CAS handled authentication.
In the following sections we will discuss some (optional) more advanced configurations.

Single Logout

The CAS protocol supports Single Logout and can be easily added to your Spring Security configuration.
Below are updates to the Spring Security configuration that handle Single Logout

<security:httpentry-point-ref="casEntryPoint">
...
<security:logoutlogout-success-url="/cas-logout.jsp"/><security:custom-filterref="requestSingleLogoutFilter"before="LOGOUT_FILTER"/><security:custom-filterref="singleLogoutFilter"before="CAS_FILTER"/></security:http><!-- This filter handles a Single Logout Request from the CAS Server --><beanid="singleLogoutFilter"class="org.jasig.cas.client.session.SingleSignOutFilter"/><!-- This filter redirects to the CAS Server to signal Single Logout should be performed --><beanid="requestSingleLogoutFilter"class="org.springframework.security.web.authentication.logout.LogoutFilter"><constructor-argvalue="https://localhost:9443/cas/logout"/><constructor-arg><beanclass=
"org.springframework.security.web.authentication.logout.SecurityContextLogoutHandler"/></constructor-arg><propertyname="filterProcessesUrl"value="/logout/cas"/></bean>

The logout element logs the user out of the local application, but does not terminate the session with the CAS server or any other applications that have been logged into.
The requestSingleLogoutFilter filter will allow the URL of /spring_security_cas_logout to be requested to redirect the application to the configured CAS Server logout URL.
Then the CAS Server will send a Single Logout request to all the services that were signed into.
The singleLogoutFilter handles the Single Logout request by looking up the HttpSession in a static Map and then invalidating it.

It might be confusing why both the logout element and the singleLogoutFilter are needed.
It is considered best practice to logout locally first since the SingleSignOutFilter just stores the HttpSession in a static Map in order to call invalidate on it.
With the configuration above, the flow of logout would be:

The user requests /logout which would log the user out of the local application and send the user to the logout success page.

The logout success page, /cas-logout.jsp, should instruct the user to click a link pointing to /logout/cas in order to logout out of all applications.

On the CAS Server side, the CAS single logout URL then submits single logout requests to all the CAS Services.
On the CAS Service side, JASIG’s SingleSignOutFilter processes the logout request by invaliditing the original session.

When using the SingleSignOutFilter you might encounter some encoding issues.
Therefore it is recommended to add the CharacterEncodingFilter to ensure that the character encoding is correct when using the SingleSignOutFilter.
Again, refer to JASIG’s documentation for details.
The SingleSignOutHttpSessionListener ensures that when an HttpSession expires, the mapping used for single logout is removed.

Authenticating to a Stateless Service with CAS

This section describes how to authenticate to a service using CAS.
In other words, this section discusses how to setup a client that uses a service that authenticates with CAS.
The next section describes how to setup a stateless service to Authenticate using CAS.

Configuring CAS to Obtain Proxy Granting Tickets

In order to authenticate to a stateless service, the application needs to obtain a proxy granting ticket (PGT).
This section describes how to configure Spring Security to obtain a PGT building upon thencas-st[Service Ticket Authentication] configuration.

The first step is to include a ProxyGrantingTicketStorage in your Spring Security configuration.
This is used to store PGT’s that are obtained by the CasAuthenticationFilter so that they can be used to obtain proxy tickets.
An example configuration is shown below

<!--
NOTE: In a real application you should not use an in memory implementation.
You will also want to ensure to clean up expired tickets by calling
ProxyGrantingTicketStorage.cleanup()
--><beanid="pgtStorage"class="org.jasig.cas.client.proxy.ProxyGrantingTicketStorageImpl"/>

The next step is to update the CasAuthenticationProvider to be able to obtain proxy tickets.
To do this replace the Cas20ServiceTicketValidator with a Cas20ProxyTicketValidator.
The proxyCallbackUrl should be set to a URL that the application will receive PGT’s at.
Last, the configuration should also reference the ProxyGrantingTicketStorage so it can use a PGT to obtain proxy tickets.
You can find an example of the configuration changes that should be made below.

The last step is to update the CasAuthenticationFilter to accept PGT and to store them in the ProxyGrantingTicketStorage.
It is important the proxyReceptorUrl matches the proxyCallbackUrl of the Cas20ProxyTicketValidator.
An example configuration is shown below.

Calling a Stateless Service Using a Proxy Ticket

Now that Spring Security obtains PGTs, you can use them to create proxy tickets which can be used to authenticate to a stateless service.
The CAS sample application contains a working example in the ProxyTicketSampleServlet.
Example code can be found below:

Proxy Ticket Authentication

The CasAuthenticationProvider distinguishes between stateful and stateless clients.
A stateful client is considered any that submits to the filterProcessUrl of the CasAuthenticationFilter.
A stateless client is any that presents an authentication request to CasAuthenticationFilter on a URL other than the filterProcessUrl.

Because remoting protocols have no way of presenting themselves within the context of an HttpSession, it isn’t possible to rely on the default practice of storing the security context in the session between requests.
Furthermore, because the CAS server invalidates a ticket after it has been validated by the TicketValidator, presenting the same proxy ticket on subsequent requests will not work.

One obvious option is to not use CAS at all for remoting protocol clients.
However, this would eliminate many of the desirable features of CAS.
As a middle-ground, the CasAuthenticationProvider uses a StatelessTicketCache.
This is used solely for stateless clients which use a principal equal to CasAuthenticationFilter.CAS_STATELESS_IDENTIFIER.
What happens is the CasAuthenticationProvider will store the resulting CasAuthenticationToken in the StatelessTicketCache, keyed on the proxy ticket.
Accordingly, remoting protocol clients can present the same proxy ticket and the CasAuthenticationProvider will not need to contact the CAS server for validation (aside from the first request).
Once authenticated, the proxy ticket could be used for URLs other than the original target service.

This section builds upon the previous sections to accommodate proxy ticket authentication.
The first step is to specify to authenticate all artifacts as shown below.

The next step is to specify serviceProperties and the authenticationDetailsSource for the CasAuthenticationFilter.
The serviceProperties property instructs the CasAuthenticationFilter to attempt to authenticate all artifacts instead of only ones present on the filterProcessUrl.
The ServiceAuthenticationDetailsSource creates a ServiceAuthenticationDetails that ensures the current URL, based upon the HttpServletRequest, is used as the service URL when validating the ticket.
The method for generating the service URL can be customized by injecting a custom AuthenticationDetailsSource that returns a custom ServiceAuthenticationDetails.

You will also need to update the CasAuthenticationProvider to handle proxy tickets.
To do this replace the Cas20ServiceTicketValidator with a Cas20ProxyTicketValidator.
You will need to configure the statelessTicketCache and which proxies you want to accept.
You can find an example of the updates required to accept all proxies below.

13.8 X.509 Authentication

13.8.1 Overview

The most common use of X.509 certificate authentication is in verifying the identity of a server when using SSL, most commonly when using HTTPS from a browser.
The browser will automatically check that the certificate presented by a server has been issued (ie digitally signed) by one of a list of trusted certificate authorities which it maintains.

You can also use SSL with "mutual authentication"; the server will then request a valid certificate from the client as part of the SSL handshake.
The server will authenticate the client by checking that its certificate is signed by an acceptable authority.
If a valid certificate has been provided, it can be obtained through the servlet API in an application.
Spring Security X.509 module extracts the certificate using a filter.
It maps the certificate to an application user and loads that user’s set of granted authorities for use with the standard Spring Security infrastructure.

You should be familiar with using certificates and setting up client authentication for your servlet container before attempting to use it with Spring Security.
Most of the work is in creating and installing suitable certificates and keys.
For example, if you’re using Tomcat then read the instructions here http://tomcat.apache.org/tomcat-6.0-doc/ssl-howto.html.
It’s important that you get this working before trying it out with Spring Security

subject-principal-regex.
The regular expression used to extract a username from the certificate’s subject name.
The default value is shown above.
This is the username which will be passed to the UserDetailsService to load the authorities for the user.

user-service-ref.
This is the bean Id of the UserDetailsService to be used with X.509.
It isn’t needed if there is only one defined in your application context.

The subject-principal-regex should contain a single group.
For example the default expression "CN=(.*?)," matches the common name field.
So if the subject name in the certificate is "CN=Jimi Hendrix, OU=…​", this will give a user name of "Jimi Hendrix".
The matches are case insensitive.
So "emailAddress=(.?)," will match "EMAILADDRESS=[email protected],CN=…​" giving a user name "[email protected]".
If the client presents a certificate and a valid username is successfully extracted, then there should be a valid Authentication object in the security context.
If no certificate is found, or no corresponding user could be found then the security context will remain empty.
This means that you can easily use X.509 authentication with other options such as a form-based login.

13.8.3 Setting up SSL in Tomcat

There are some pre-generated certificates in the samples/certificate directory in the Spring Security project.
You can use these to enable SSL for testing if you don’t want to generate your own.
The file server.jks contains the server certificate, private key and the issuing certificate authority certificate.
There are also some client certificate files for the users from the sample applications.
You can install these in your browser to enable SSL client authentication.

To run tomcat with SSL support, drop the server.jks file into the tomcat conf directory and add the following connector to the server.xml file

clientAuth can also be set to want if you still want SSL connections to succeed even if the client doesn’t provide a certificate.
Clients which don’t present a certificate won’t be able to access any objects secured by Spring Security unless you use a non-X.509 authentication mechanism, such as form authentication.

13.9 Run-As Authentication Replacement

13.9.1 Overview

The AbstractSecurityInterceptor is able to temporarily replace the Authentication object in the SecurityContext and SecurityContextHolder during the secure object callback phase.
This only occurs if the original Authentication object was successfully processed by the AuthenticationManager and AccessDecisionManager.
The RunAsManager will indicate the replacement Authentication object, if any, that should be used during the SecurityInterceptorCallback.

By temporarily replacing the Authentication object during the secure object callback phase, the secured invocation will be able to call other objects which require different authentication and authorization credentials.
It will also be able to perform any internal security checks for specific GrantedAuthority objects.
Because Spring Security provides a number of helper classes that automatically configure remoting protocols based on the contents of the SecurityContextHolder, these run-as replacements are particularly useful when calling remote web services

The first method returns the Authentication object that should replace the existing Authentication object for the duration of the method invocation.
If the method returns null, it indicates no replacement should be made.
The second method is used by the AbstractSecurityInterceptor as part of its startup validation of configuration attributes.
The supports(Class) method is called by a security interceptor implementation to ensure the configured RunAsManager supports the type of secure object that the security interceptor will present.

One concrete implementation of a RunAsManager is provided with Spring Security.
The RunAsManagerImpl class returns a replacement RunAsUserToken if any ConfigAttribute starts with RUN_AS_.
If any such ConfigAttribute is found, the replacement RunAsUserToken will contain the same principal, credentials and granted authorities as the original Authentication object, along with a new SimpleGrantedAuthority for each RUN_AS_ConfigAttribute.
Each new SimpleGrantedAuthority will be prefixed with ROLE_, followed by the RUN_ASConfigAttribute.
For example, a RUN_AS_SERVER will result in the replacement RunAsUserToken containing a ROLE_RUN_AS_SERVER granted authority.

The replacement RunAsUserToken is just like any other Authentication object.
It needs to be authenticated by the AuthenticationManager, probably via delegation to a suitable AuthenticationProvider.
The RunAsImplAuthenticationProvider performs such authentication.
It simply accepts as valid any RunAsUserToken presented.

To ensure malicious code does not create a RunAsUserToken and present it for guaranteed acceptance by the RunAsImplAuthenticationProvider, the hash of a key is stored in all generated tokens.
The RunAsManagerImpl and RunAsImplAuthenticationProvider is created in the bean context with the same key:

By using the same key, each RunAsUserToken can be validated it was created by an approved RunAsManagerImpl.
The RunAsUserToken is immutable after creation for security reasons

13.10 Spring Security Crypto Module

13.10.1 Introduction

The Spring Security Crypto module provides support for symmetric encryption, key generation, and password encoding.
The code is distributed as part of the core module but has no dependencies on any other Spring Security (or Spring) code.

13.10.2 Encryptors

The Encryptors class provides factory methods for constructing symmetric encryptors.
Using this class, you can create ByteEncryptors to encrypt data in raw byte[] form.
You can also construct TextEncryptors to encrypt text strings.
Encryptors are thread-safe.

BytesEncryptor

Use the Encryptors.standard factory method to construct a "standard" BytesEncryptor:

Encryptors.standard("password", "salt");

The "standard" encryption method is 256-bit AES using PKCS #5’s PBKDF2 (Password-Based Key Derivation Function #2).
This method requires Java 6.
The password used to generate the SecretKey should be kept in a secure place and not be shared.
The salt is used to prevent dictionary attacks against the key in the event your encrypted data is compromised.
A 16-byte random initialization vector is also applied so each encrypted message is unique.

The provided salt should be in hex-encoded String form, be random, and be at least 8 bytes in length.
Such a salt may be generated using a KeyGenerator:

TextEncryptor

Use the Encryptors.text factory method to construct a standard TextEncryptor:

Encryptors.text("password", "salt");

A TextEncryptor uses a standard BytesEncryptor to encrypt text data.
Encrypted results are returned as hex-encoded strings for easy storage on the filesystem or in the database.

Use the Encryptors.queryableText factory method to construct a "queryable" TextEncryptor:

Encryptors.queryableText("password", "salt");

The difference between a queryable TextEncryptor and a standard TextEncryptor has to do with initialization vector (iv) handling.
The iv used in a queryable TextEncryptor#encrypt operation is shared, or constant, and is not randomly generated.
This means the same text encrypted multiple times will always produce the same encryption result.
This is less secure, but necessary for encrypted data that needs to be queried against.
An example of queryable encrypted text would be an OAuth apiKey.

13.10.3 Key Generators

The KeyGenerators class provides a number of convenience factory methods for constructing different types of key generators.
Using this class, you can create a BytesKeyGenerator to generate byte[] keys.
You can also construct a StringKeyGenerator to generate string keys.
KeyGenerators are thread-safe.

BytesKeyGenerator

Use the KeyGenerators.secureRandom factory methods to generate a BytesKeyGenerator backed by a SecureRandom instance:

The matches method returns true if the rawPassword, once encoded, equals the encodedPassword.
This method is designed to support password-based authentication schemes.

The BCryptPasswordEncoder implementation uses the widely supported "bcrypt" algorithm to hash the passwords.
Bcrypt uses a random 16 byte salt value and is a deliberately slow algorithm, in order to hinder password crackers.
The amount of work it does can be tuned using the "strength" parameter which takes values from 4 to 31.
The higher the value, the more work has to be done to calculate the hash.
The default value is 10.
You can change this value in your deployed system without affecting existing passwords, as the value is also stored in the encoded hash.

The Pbkdf2PasswordEncoder implementation uses PBKDF2 algorithm to hash the passwords.
In order to defeat password cracking PBKDF2 is a deliberately slow algorithm and should be tuned to take about .5 seconds to verify a password on your system.

// Create an encoder with all the defaults
Pbkdf2PasswordEncoder encoder = new Pbkdf2PasswordEncoder();
String result = encoder.encode("myPassword");
assertTrue(encoder.matches("myPassword", result));

13.11 Concurrency Support

In most environments, Security is stored on a per Thread basis.
This means that when work is done on a new Thread, the SecurityContext is lost.
Spring Security provides some infrastru